الحمد لله رب العالمين والصالة والسالم على خاتم

النبيين

Geometric Design ndash Basic Principles Safety for all users Functionality ndash the need for access and mobility Accessibility for people with disabilities ndash as a prerequisite to

access to employment recreation and healthcare Mutual support and compatibility between transportation

facilities and services and the adjacent land uses and associated activities they serve

Consistency with transportation plans and policies and environmental regulations that guide the community the region the province and the Federal government

Transportation facility design and operational requirements established by others

Input and participation from local constituents and the appropriate local regional and state reviewing agencies 1048708

Cost effectiveness ndash the value returned for the investments made in transportation

GEOMETRIC DESIGN ndash Course Heads

Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip

Horizontal Alignment Roadways must respect the existing and

developed environment through which they pass

As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints

Horizontal Alignment Alignment constraints typically include

Physical controls - topography watercourses geophysical conditions land use and man-made features

Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas

Economics - construction costs right-of-way costs utility impacts operating and maintenance costs

Safety - sight distance consistency of alignment human factor considerations

Highway classification and design policies - functional classification level of service design speed design standards

Introduction of curvilinear alignments is necessary when the designer encounters these constraints

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Geometric Design ndash Basic Principles Safety for all users Functionality ndash the need for access and mobility Accessibility for people with disabilities ndash as a prerequisite to

access to employment recreation and healthcare Mutual support and compatibility between transportation

facilities and services and the adjacent land uses and associated activities they serve

Consistency with transportation plans and policies and environmental regulations that guide the community the region the province and the Federal government

Transportation facility design and operational requirements established by others

Input and participation from local constituents and the appropriate local regional and state reviewing agencies 1048708

Cost effectiveness ndash the value returned for the investments made in transportation

GEOMETRIC DESIGN ndash Course Heads

Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip

Horizontal Alignment Roadways must respect the existing and

developed environment through which they pass

As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints

Horizontal Alignment Alignment constraints typically include

Physical controls - topography watercourses geophysical conditions land use and man-made features

Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas

Economics - construction costs right-of-way costs utility impacts operating and maintenance costs

Safety - sight distance consistency of alignment human factor considerations

Highway classification and design policies - functional classification level of service design speed design standards

Introduction of curvilinear alignments is necessary when the designer encounters these constraints

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

GEOMETRIC DESIGN ndash Course Heads

Cross-Section Elements Horizontal Alignment Vertical Alignment Intersections Interchanges helliphelliphelliphellip helliphelliphelliphellip

Horizontal Alignment Roadways must respect the existing and

developed environment through which they pass

As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints

Horizontal Alignment Alignment constraints typically include

Physical controls - topography watercourses geophysical conditions land use and man-made features

Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas

Economics - construction costs right-of-way costs utility impacts operating and maintenance costs

Safety - sight distance consistency of alignment human factor considerations

Highway classification and design policies - functional classification level of service design speed design standards

Introduction of curvilinear alignments is necessary when the designer encounters these constraints

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Roadways must respect the existing and

developed environment through which they pass

As a result roadways are not always flat and straight ndash they possess vertical and horizontal curves in their alignments to circumvent or be compatible with existing constraints

Horizontal Alignment Alignment constraints typically include

Physical controls - topography watercourses geophysical conditions land use and man-made features

Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas

Economics - construction costs right-of-way costs utility impacts operating and maintenance costs

Safety - sight distance consistency of alignment human factor considerations

Highway classification and design policies - functional classification level of service design speed design standards

Introduction of curvilinear alignments is necessary when the designer encounters these constraints

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Alignment constraints typically include

Physical controls - topography watercourses geophysical conditions land use and man-made features

Environmental considerations - affect on adjacent land use community impacts ecologically sensitive areas

Economics - construction costs right-of-way costs utility impacts operating and maintenance costs

Safety - sight distance consistency of alignment human factor considerations

Highway classification and design policies - functional classification level of service design speed design standards

Introduction of curvilinear alignments is necessary when the designer encounters these constraints

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Blending with the nature terrain existing features

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Horizontal alignment deals with changes in the

plan view of the roadway

Steps

Locating Laying out Highway Design Elements

bull Horizontal Curvesbull Superelevationbull Gradesbull helliphelliphelliphellip

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

First Step

Existing topographical construction environmental and other constraints should be identified on the base map to assist the designer in minimizing impacts to wetlands historical and archaeological features private and protected property and permanent structures

To the extent possible these constraints should serve as boundaries through which the designer must fit the geometry

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Locating Highway

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Locating Highway

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

Horizontal alignment should be as smooth and as direct as possible and responsive to the topography Flatter curvature with shorter tangents is generally preferable to sharp curves connected by long tangents Angle points should be avoided

Where possible geometry should be concentric with andor parallel to the existing roadway layouts so that new impacts to the surrounding area are minimized

Alignment should generally conform to the natural contours A line cutting across the contours involves high fills and deep cuts mars the landscape and is difficult for the maintenance

The number of curves should in general be kept to the minimum

The alignment should avoid abrupt changes turns

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

Abrupt reversals in alignment and sharp curvature on long high fills should be avoided bull In Hilly areas

Curves with small deflection angles (5 degrees or less) should be long enough to avoid the appearance of a kink bull Curves should be 500 feet long for a central angle of 5 degrees and

increased 100 feet for each degree decrease in central anglebull The minimum length of horizontal curves (Lc) should be

bull Lc desirable = 30V (high speed controlled-access facilities) bull Lc minimum = 15V (other arterials)

bull (Where V = design speed in miles per hour) Broken back curvature (a short tangent between two

curves in same direction) should be avoided because drivers do not expect to encounter this arrangement on typical highway geometry

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

Except for use in entrance andor exit ramps the use of compound curvature should be avoided since drivers do not expect to encounter this arrangement on typical highway geometry

If compound circular curves are required in an effort to fit the highway to the terrain and other constraints large differences in radius should be avoided The radius of the largest curve should not be more that 15 time the radius of the smaller curve (except for highway ramps) On ramps the ratio of the larger curve to the smaller curve should not exceed 21

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

The horizontal alignment should be in balance with the vertical profile and cross section rotation associated with superelevation This is accomplished through the use of a cross sectional analysis Under this analysis procedure the alignment is plotted onto the cross section to the lines and grades dictated by the geometry

Horizontal curves should be avoided on bridges whenever possible These cause design construction and operational problems Where a curve is necessary on a bridge a simple curve should be used on the bridge and any curvature or superelevation transitions placed on the approaching roadway

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment Locating Highway

Should the impacts on the existing topography private property environmental areas etc be significant for successive cross sections then modification to the vertical and horizontal geometry should be considered to minimize the impacts thereby optimizing a balanced geometric design

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Alignment

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Practice Session

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

5 10 15 20 25 30 35 40 45

5

10

15

20

25

30

35

40

45

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

500

1000

1500

2000

2500

3000

3500

4000

4500

3-D Model

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

MURREE HILLS

SIMLY DAM

DTM of Murree Hills

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

-1 00 000 100 200 300 400 500 600 700 800 900 1000-100

000

100

200

300

400

500

600

700

800

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

360

380

400

420

440

460

480

500

520

540

560

580

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

National Forest Boundary

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Straight segments are called Tangents Horizontal curves help change from one

tangent to another

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Design Elements Curves

Simple Circular Curves Compound Curves Broken Back Curves S Curves Transition Curves

Which one to be used where and how

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Simple Circular

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Compound Curves

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Horizontal curves are circular to minimize

steering effort Curves need to be long enough to avoid unsafe

or uncomfortable conditions Additional features can help reduce the driving

effortbull ndash Super Elevationbull ndash Transition (or spiral) curves which slowly

transition from an infinite radius (a tangent) to the radius of the circular curve

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Rmin = ___V2______

15(e + f) Where Rmin is the minimum radius in feet

V = velocity (mph) e = superelevation f = friction (15 = gravity and unit conversion)

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curvesbull Rmin uses max e and max f (defined by AASHTO DOT and

graphed in Green Book) and design speed

bull f is a function of speed roadway surface weather condition tire condition and based on comfort ndash drivers brake make sudden lane changes and change position within a lane when acceleration around a curve becomes ldquouncomfortablerdquo

bull AASHTO 05 20 mph with new tires and wet pavement to 035 60 mph

bull f decreases as speed increases (less tirepavement contact)

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Max e Controlled by 4 factors

bull Climate conditions (amount of ice and snow)bull Terrain (flat rolling mountainous)bull Type of area (rural or urban)bull Frequency of slow moving vehicles who might be

influenced by high super elevation rates

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves Max e

bull Highest in common use = 10 12 with no ice and snow on low volume gravel-surfaced roads

bull 8 is logical maximum to minimize slipping by stopped vehicles considering snow and ice

bull Iowa uses a maximum of 6 on new projectsbull For consistency use a single rate within a project or

on a highway

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curves

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curve Sight Distance

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50

Horizontal Curve Sight Distance

• Slide 1
• Geometric Design ndash Basic Principles
• GEOMETRIC DESIGN ndash Course Heads
• Horizontal Alignment
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Locating Highway
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Practice Session
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Curves
• Design Elements
• Slide 32
• Slide 33
• Slide 34
• Slide 35
• Slide 36
• Slide 37
• Slide 38
• Slide 39
• Slide 40
• Slide 41
• Horizontal Curves
• Slide 43
• Slide 44
• Slide 45
• Slide 46
• Slide 47
• Slide 48
• Horizontal Curve Sight Distance
• Slide 50