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Ministry of Public Works

Roads Administration

Design Manual for Roads and Bridges

Edition 3, January 2011

The Design Manual for Roads and Bridges is divided into four separate parts.Please refer to the relevant part for a table of contents.

PART 1 - Kuwait Highway Design Manual

PART 2 - Kuwait Bridges and Highway Structures Design Manual

PART 3 - Kuwait Highway Drainage Design Manual

PART 4 - Standard Drawings

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Preamble

This Roads and Bridges Design Manual was

prepared by the Ministry of Public Works

Roads Sector in cooperation with Kuwait

Municipality and the Ministry of Interior.

.

This Manual shall be used as a guide for the

design of Roads and Bridges in the State of

Kuwait. It will be the responsibility of the

designer to ensure that the guidelines

contained in this manual are applied properly

and modified where appropriate to meet the

approved standards of engineering and safety,

subject to the obtaining the necessary

approvals.

.

" .

This Manual shall be read together with typical

drawings of the MPW Roads Sector.

The Designer shall obtain approval for the

design from all relevant authorities, including

Ministry of Public Works, Ministry of Interior

and Kuwait Municipality.

.

The Ministry of Public Works intends to update

this Manual on regular basis and welcomes

any suggestions for improvements. All

suggestions and requests for clarifications

shall be forwarded to the Assistant

Undersecretary of the Roads Administration.

.

.

.

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Ministry of Public WorksRoads Administration

PART 1Kuwait Highway Design Manual

Edition 2

January 2011

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Kuwait Bridges and Highway Structures Design Manual Table of Contents

Part 1 Kuwait Highway Design Manual

Page i

TABLE OF CONTENTS

1. HIGHWAY CLASSIFICATION .....................................................................................................1-1

1.1 Kuwait Road Hierarchy ............................................ ......................................... ........... 1-1

1.2 Determining the Road Class .......................................................................................... 1-4

1.3 Local Roads ................................................................................................................ 1-5

1.4 Collector Roads ........................................................................................................... 1-5

1.5 Arterial Roads ............................................................................................................. 1-5

1.6 Expressways and Freeways ........................................................................................... 1-5

2. TRAFFIC ............................................................................................................................. 2-1

2.1 Introduction ............................................................................................................... 2-1

2.2 Definitions .................... ......................................... ................................ .................... 2-1

2.3 Level of Service (LoS) .................................................................................................. 2-1

2.4 Design Vehicles .......................................................................................................... 2-7

2.5 Pedestrians ................................................................................................................ 2-7

3. DESIGN SPEED ..................................................................................................................... 3-1

3.1 General ...................................................................................................................... 3-1

3.2 Selection of Design Speed ............................................................................................. 3-1

3.3 Effect of Terrain ................... ......................................... ......................................... ...... 3-2

3.4 Relationship with Posted Speed ...................................... ......................................... ...... 3-2

3.5 Existing Roads ............................................................................................................ 3-2

3.6 Locations where Design Speed Changes ............. ......................................... .................... 3-2

3.7 Interchanges .............................................................................................................. 3-3

3.8 Reduction below Standards ........................................................................................... 3-3

4. SIGHT DISTANCE .................................................................................................................. 4-1

4.1 General ..................................................................................................................... 4-1

4.2 Eye-Height and Object Height ................. .................................................. .................... 4-1

4.3 Stopping Sight Distance (SSD) .................................. ......................................... ........... 4-1

4.4 Passing Sight Distance (PSD) .................................... ......................................... ........... 4-1

4.5 Decision Sight Distance (DSD) .. ................................ ......................................... ........... 4-3

4.6 Maintaining Sight Distances ........................................... ......................................... ...... 4-4

4.7 Provision of Passing Sight Distance ............... .................................................. ............... 4-4

5. HORIZONTAL ALIGNMENT ....................................................................................................... 5-1

5.1 General ..................................................................................................................... 5-1

5.2 Maximum Super elevation ............................................................................................. 5-1

5.3 Minimum Curvature ........................................ ......................................... .................... 5-2

5.4 Transition Curves ........................................................................................................ 5-4

5.5 Widening on Curves ..................................................... ......................................... .... 5-10

5.6 Sight Distance on Horizontal Curves .............................................................................. 5-10

5.7 Visual Appearance of Horizontal Geometry .................................................. .................. 5-14

5.8 Horizontal Curves on Local Streets ............................................................................... 5-17

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Page ii

6. VERTICAL ALIGNMENT .......................................................................................................... 6-1

6.1 General ..................................................................................................................... 6-1

6.2 Vertical Curves ........................................................................................................... 6-2

6.3 Maximum Gradient ...................................................................................................... 6-4

6.4 Minimum Gradient ...................................................................................................... 6-5

6.5 Visibility .................................................................................................................... 6-5

6.6 Choice of Longitudinal Profile ....................... .................................................. ............... 6-5

6.7 Visual Appearance of Vertical Geometry .......................................................................... 6-5

6.8 Combining Horizontal and Vertical Alignment ................................................................... 6-6

6.9 Vertical Clearances ..................................................................................................... 6-7

6.10 Local Roads ................................................................................................................ 6-9

7. CROSS-SECTIONAL ELEMENTS ................................................................................................ 7-1

7.1 General ..................................................................................................................... 7-1

7.2 Limits of Right of Way .................................................................................................. 7-1

7.3 Side Slopes ................... ......................................... ......................................... ........... 7-2

7.4 Verges ...................................................................................................................... 7-2

7.5 Service Reservations ...................................... ......................................... .................... 7-3

7.6 Shoulders and Curb Clearances ...................................... ......................................... ...... 7-3

7.7 Clearances to Structures .......................................... ......................................... ........... 7-4

7.8 Clearances to Safety Barriers ....................... .................................................. ............... 7-5

7.9 Lane Widths ............................................................................................................... 7-5

7.10 Median Widths ............................................................................................................ 7-6

7.11 Cross Slopes .............................................................................................................. 7-7

7.12 Gutters and Drainage Ditches ........................................................................................ 7-8

7.13 Other Elements within the Cross-Section .. .................................................. .................... 7-8

7.14 Tunnels ...................................................................................................................... 7-9

8. HIGHWAY FACILITIES ........................................................................................................... 8-1

8.1 General ..................................................................................................................... 8-1

8.2 Pedestrian Facilities ..................................................................................................... 8-1

8.3 Public Transport Facilities .............................................. ......................................... ...... 8-5

8.4 Parking Facilities ......................................................................................................... 8-6

8.5 Curbs ........................................................................................................................ 8-8

8.6 Fences ....................................................................................................................... 8-8

8.7 Safety Barriers ........................................................................................................... 8-9

8.8 Energy Absorbing Barriers ................. ....................... ......................................... ......... 8-12

8.9 Traffic Calming ................... ......................................... ......................................... .... 8-14

8.10 Landscaping ............................................................................................................. 8-18

8.11 Utilities .................................................................................................................... 8-19

9. LOCAL ROADS ..................................................................................................................... 9-1

9.1 Introduction ............................................................................................................... 9-1

9.2 Basic Design Parameters ............................................... ......................................... ...... 9-1

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Page iii

9.3 Intersections .............................................................................................................. 9-4

9.4 Pedestrian Facilities ............................... .................................................. .................... 9-4

9.5 Traffic Calming ........................................................................................................... 9-4

9.6 Turning Areas ..................... ......................................... ......................................... ...... 9-4

9.7 Driveways .............................. ................................ ......................................... ........... 9-4

9.8 Summary of Design Parameters ..................................................................................... 9-4

10. COLLECTOR ROADS ............................................................................................................ 10-1

10.1 Introduction ....................................................................................................................... 10-1

10.2 Basic Design Parameters ..................................................................................................... 10-1

10.3 Intersections ...................................................................................................................... 10-3

10.4 Pedestrian Facilities ............................................................................................................ 10-3

10.5 Traffic Calming ................................................................................................................... 10-3

10.6 Summary of Design Parameters .......................................................................................... 10-3

11. ARTERIAL ROADS .............................................................................................................. 11-1

11.1 Introduction ....................................................................................................................... 11-1


11.3 Intersections ...................................................................................................................... 11-2

11.4 Service Roads .................................................................................................................... 11-2



12. EXPRESSWAYS AND FREEWAYS ............................................................................................. 12-1

12.1 Introduction ....................................................................................................................... 12-1


12.3 Intersections ...................................................................................................................... 12-3

12.4 Service Roads .................................................................................................................... 12-3



13. INTERSECTIONS GENERAL ................................................................................................. 13-1

13.1 Introduction ....................................................................................................................... 13-1

13.2 Intersection Spacing ........................................................................................................... 13-1

13.3 Selection of Intersection Type .............................................................................................. 13-2

13.4 Choosing between Roundabouts and Signalized Intersections ................................................. 13-2

13.5 Design Vehicles .................................................................................................................. 13-5

13.6 Siting of Intersections ......................................................................................................... 13-5

13.7 Intersection Types (1) - Major / Minor Intersections .............................................................. 13-5

13.8 Intersection Types (2) - Roundabouts .................................................................................. 13-7

13.9 Intersection Types (3) - U-turns .......................................................................................... 13-8

13.10Intersection Types (4) - Signalized Intersections ................................................................... 13-8

13.11Intersection Types (5) - Interchanges .................................................................................. 13-9

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Page iv

14. AT GRADE INTERSECTIONS .................................................................................................. 14-1

14.1 Introduction ....................................................................................................................... 14-1

14.2 Safety ............................................................................................................................... 14-1

14.3 Types of At-Grade Intersections ........................................................................................... 14-1

14.4 Capacity ............................................................................................................................ 14-5

14.5 Pedestrian Considerations ................................................................................................... 14-6

14.6 Alignment .......................................................................................................................... 14-6

14.7 Visibility ............................................................................................................................. 14-6

14.8 Corner Radii ....................................................................................................................... 14-8

14.9 Lane Widths ..................................................................................................................... 14-10

14.10Islands ............................................................................................................................ 14-11

14.11Tapers ............................................................................................................................. 14-12

14.12Right-Turning Roadways ................................................................................................... 14-14

14.13Deceleration and Queuing ................................................................................................. 14-15

14.14Turning Length ................................................................................................................. 14-16

14.15Staggered T-intersection Spacing ....................................................................................... 14-16

14.16Drainage ......................................................................................................................... 14-17

14.17Summary of Design Process .............................................................................................. 14-17

15. ROUNDABOUTS .................................................................................................................. 15-1

15.1 Introduction ....................................................................................................................... 15-1

15.2 Types of Roundabouts ......................................................................................................... 15-2

15.3 Location of Roundabouts ..................................................................................................... 15-8

15.4 Design Process ................................................................................................................... 15-9

15.5 Capacity of Roundabouts ................................................................................................... 15-10

15.6 Geometric Design of Roundabouts ..................................................................................... 15-12

15.7 Cross Fall & Drainage ........................................................................................................ 15-27

15.8 Segregated Right Turn Lanes ............................................................................................. 15-30

15.9 Safety of Roundabouts ...................................................................................................... 15-36

16. U-TURNS ......................................................................................................................... 16-1

16.1 General ............................................................................................................................. 16-1

16.2 Entry Taper ........................................................................................................................ 16-2

16.3 Deceleration Length ............................................................................................................ 16-3

16.4 Queue Length and Protected Length ..................................................................................... 16-3

16.5 Channelizing Nose Width ..................................................................................................... 16-3

16.6 Reduced Median Width ........................................................................................................ 16-3

16.7 U-turn Lane Width .............................................................................................................. 16-3

16.8 Median Width ..................................................................................................................... 16-3

16.9 Mouth Treatment ................................................................................................................ 16-4

16.10Summary .......................................................................................................................... 16-4

16.11U-turn Diameter ................................................................................................................. 16-4

16.12Median Widening ................................................................................................................ 16-5

16.13Local Bulbing ..................................................................................................................... 16-5

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Page v

17. SIGNALIZED INTERSECTIONS ............................................................................................... 17-1

17.1 General ............................................................................................................................. 17-1

17.2 Applicability of Major / Minor Intersection Principles ............................................................... 17-1

17.3 Specific Requirements at Signalized Intersections .................................................................. 17-1

17.4 Width of Medians ................................................................................................................ 17-1

17.5 Size of Islands .................................................................................................................... 17-2

17.6 Vehicular Swept Paths ........................................................................................................ 17-2

17.7 Location of Pedestrian Crossing Facilities .............................................................................. 17-3

17.8 Width of Pedestrian Crossing Facilities .................................................................................. 17-3

17.9 Designing for Queue Lengths in Left-turning Lanes ................................................................ 17-3

17.10Signalized Roundabouts ...................................................................................................... 17-4

17.11U-turns at Signalized Intersections ....................................................................................... 17-4

18. GRADE SEPARATIONS AND INTERCHANGES .............................................................................. 18-1

18.1 Introduction ....................................................................................................................... 18-1

18.2 Types of Interchange .......................................................................................................... 18-1

18.3 Selection of Interchange Type ........................................................................................... 18-13

18.4 Design Speed .................................................................................................................. 18-15

18.5 Lane Provision ................................................................................................................... 18-15

18.6 Selection of Layout Type .................................................................................................... 18-16

18.7 Single-Lane Entrances ....................................................................................................... 18-17

18.8 Single-Lane Exits ............................................................................................................... 18-19

18.9 Two-Lane Entrances .......................................................................................................... 18-22

18.10Two-Lane Exits.................................................................................................................. 18-22

18.11Connecting Roadways ....................................................................................................... 18-26

18.12Spacing of Merges and Diverges ........................................................................................ 18-27

18.13Weaving .......................................................................................................................... 18-28

18.14Link Roads ....................................................................................................................... 18-29

18.15Other Design Considerations ............................................................................................. 18-29

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Kuwait Bridges and Highway Structures Design Manual Chapter 1

Part 1 Kuwait Highway Design Manual Highway Classification

Page 1-3

Figure 1.2: Road Hierarchy in Kuwait2

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Page 1-4

Table 1.2: Characteristics of Roads by Class

Local Roads Collector Roads Arterial RoadsExpresswaysand Freeways

Land service Land access theprimary consideration

Land access and trafficmovement of equalimportance

Land access asecondaryconsideration

No access or

restricted accessfrom serviceroads

Traffic service

Trafficmovement the

secondaryconsideration

Land access and trafficmovement of equalimportance

Trafficmovement the

primaryconsideration

Optimum mobility

TypicalIntersection spacing

Urban: as required

Rural: >l00m>100m

Urban: >200m

Rural: >1.5km

Urban: >1km

Rural: >2km

Nature of traffic flow Interrupted flow Interrupted flowUninterruptedflow except atintersections

Free flow

Vehicle typePassenger and servicevehicles**

All types except semi-trailers and above*

All types All types

Connect toCollector RoadsLocal Roads

Arterial RoadsCollector Roads

Local Roads

Expressways and

FreewaysArterial Roads

Collector Roads

Expressways andFreeways Arterial

Roads

*In industrial areas, Collector Roads should accommodate all types of vehicle

**In industrial and in rural areas, trucks may have to be catered for.

Speed limits on roads may differ, even within the same class of road. In selecting the posted speed, that is,

the speed limit displayed to drivers by means of road signs, it is normal practice to undertake a vehicle

speed survey, and to adopt a value close to the observed 85th-percentile speed.

1.2 DETERMINING THE ROAD CLASS

In Kuwait, it is the planners role to review and determine the road class and the width of the right of way.

Given this information, the highway designer should review the traffic volumes and the functional

requirements of the road, and then determine the appropriate standards for all elements of highway

provision in accordance with the guidance contained in this manual.

In areas where new development is taking place, it may be beneficial for the works to be phased, possibly

providing a lower and interim standard of provision while always ensuring that the ultimate configuration

can be achieved. Similarly, where redevelopment of an existing area occurs, it is important that the class

of the road be reviewed to check whether its status has been affected by the redevelopment.

The design details and facilities to be provided on a road are not entirely dictated by its class. The cross

section for a collector road for example, may vary from a one-way street to a four-lane divided road. The

geometric design of the road is affectedby the following factors:

Design speed

Design vehicles

Composition of the traffic stream

Pedestrians

Safety

Traffic volume

Adjacent land use

Climatic conditions

Terrain

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Page 1-5

Economics of the area

Aesthetics

Sociological factors

Public preferences

In certain areas of Kuwait, it is particularly difficult to classify roads from their adjacent land use, andtherefore at some locations roads may not display the characteristics typical of their class. For example,

the number of accesses may be higher than average, more parking may occur, or there may be a greater

than normal number of intersections. Should the designer consider that the road class is inappropriate

under the specific circumstances, he should review and agree the class with both the Ministry of Public

Works and Kuwait Municipality.

The following sections introduce each of the classes used in Kuwait.

1.3 LOCAL ROADS

A significant percentage of a city network comprises local roads, which are designed to allow vehicles to

reach the frontage of properties from a collector or arterial road. The main function of local roads is to

provide land access, and they generally carry low volumes of traffic. They serve residential, commercial or

industrial land uses. Trips made on local roads will generally have an origin or destination actually on the

local road or in immediately adjoining areas. In planning the layout of a local road network, care should betaken to avoid creating routes which could be attractive to through traffic, or which encourage high speeds

to the detriment of safety.

As this is the lowest class in the road hierarchy, direct access is permitted to all abutting properties.

Local roads can be grouped into two categories, rural local roads and urban local streets.

1.4 COLLECTOR ROADS

The function of collector roads is to collect traffic, from local roads to arterial roads, and to distribute traffic

flow from arterial roads back to the local roads. Access to properties is normally allowed on collector roads.

In rural areas, the function of collector road is twofold, to provide access to adjacent land and to carry

traffic into areas with sparse development.

1.5 ARTERIAL ROADSArterial roads are of a lower design standard than Expressways and Freeways. Their intersections with other

arterial roads and lower class roads can be either grade-separated or at grade (roundabouts or signalized).

Arterial roads are intended to carry large volumes of traffic moving at medium to high speed, and are used

by a broad range of vehicle types, because they distribute traffic from the higher class roads to the lower

class roads and vice versa.

1.6 EXPRESSWAYS AND FREEWAYS

Expressways and Freeways are designed to move heavy volumes of high-speed traffic (under free flowing

conditions). Expressways and Freeways form only a small percentage of the roads in the road network, but

they perform a crucial role in segregating fast through traffic from slower moving local traffic. High traffic

volumes generate the need for a Special Road, which in turn necessitates fully controlled access. This is

achieved with either grade-separated interchanges or service roads that serve land adjacent to the highway

and connect to the main line by free-flow ramps.

In rural situations, the function of Expressways and Freeways is to connect major cities or industrial areas,

and to provide the major routes for international traffic movements.

In urban areas, the function is to provide high-standard routes connecting areas of major traffic generation.

____________________

1Third Kuwait Master Plan Review.

2Kuwait Manual on Traffic Control Devices, 2011.

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Part 1 Kuwait Highway Design Manual Traffic

Page 2-1

2 TRAFFIC

2.1 INTRODUCTION

The volume of traffic that will use a new road facility is the major determinant of the scale of provision. It is

important therefore that a robust estimate of future vehicle usage of the road is available to the designer at

the outset. It is normal to select a Design Year which typically may be fifteen to twenty years after the

opening of the road.

For a given traffic flow and the purpose of the road, the designer can identify its class, for example

Expressway and Freeway Network, Arterial or Collector. Factors such as the number of lanes and the type

and scale of the interchanges or intersections influence the ease of use of the road, and its ability to

perform its function satisfactorily.

This matter is dealt with by the concept of Level of Service, and it is normal practice for a new facility to be

designed to have a high Level of Service (that is to say, to have very significant spare capacity) in its

opening year, but to have much lower Level of Service (nearing capacity) at the end of its design period.

In order to discuss this further, it is necessary to introduce some definitions.

2.2 DEFINITIONS

Definitions of the terms used in this section of the manual can be found in the Glossary. The readers

attention is particularly drawn to the definitions of the following terms:

Prevailing Road Conditions

Prevailing Traffic Conditions

Capacity

Traffic Volume

Annual Average Daily Traffic (AADT)

30th-highest Hourly Volume (30 HV)

Design Hour Volume (DHV)

Design Speed

Operating Speed Level of Service (LoS)

Service Flow Rate

Free Flow Speed (FFS)

2.3 LEVEL OF SERVICE (LOS)

Level of Service is a quality measure describing operational conditions within a stream.

LoS takes account of many factors, including:

Speed

Travel time

Traffic interruptions

Freedom to maneuver; that is, to change lane, accelerate or decelerate.

Driving comfort, which is subjective and depends on the perception of each individual driver.

Six levels of Service A, B, C, D, E and F are defined in Highway Capacity Manual for Urban Streets,

Signalized Intersections, Un-signalized Intersections, Pedestrians, Bicycles, Two Lanes Highways, Multilane

Highways, Freeways, Ramps, and Transit facilities. Level A is the highest and level F is the lowest. The

lower the Level of Service, the greater is the traffic density, and the higher is the likelihood of delays

occurring through the interaction of vehicles within the traffic stream. In this chapter Level of Service

concepts are presented for Expressway and Freeway sections and pedestrian facilities, for other facilities the

reader is advised to refer to HCM 20001.

The characteristics of each LoS band for a motorway section are shown in Table 2.1.

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Page 2-2

Table 2.1: Characteristics of Level of Service for Expressway and Freeway Sections

CriteriaLOS

A B C D E

FFS = 120 km/h

Maximum density (pcu/km/ln) 7 11 16 22 28

Maximum v/c 0.35 0.55 0.77 0.92 1.00

Maximum Service flow rate

(pcu/km/ln)840 1320 1840 2200 2400

FFS = 110 km/h


Maximum v/c 0.33 0.51 0.70 0.91 1.00


(pcu/h/ln)770 1210 1740 2135 2300

FFS = 100 km/h


Maximum v/c 0.30 0.48 0.70 0.90 1.00


(pcu/h/ln)700 1100 1600 2065 2300

FFS = 90 km/h


Maximum v/c 0.28 0.44 0.64 0.87 1.00


(pcu/h/ln)630 990 1440 1955 2250

Source: Highway Capacity Manual1

Operating characteristics for the six LoS are shown in Plate 2.1 to Plate 2.6. The LoS are defined to

represent reasonable ranges in the three critical flow variables: speed, density, and flow rate.

LoS A describes free-flow operations. Free-flow speeds prevail and vehicles are almost completely

unimpeded in their ability to maneuver within the traffic stream. The effects of incidents or point

breakdowns are easily absorbed at this level.

LoS B represents reasonably free flow, and free-flow speeds are maintained. The ability to maneuver within

the traffic stream is only slightly restricted, and the general level of physical and psychological comfort

provided to drivers is still high. The effects of minor incidents and point breakdowns are still easily

absorbed.

LoS C provides for flow with speeds at or near the FFS of the freeway. Freedom to maneuver within the

traffic stream is noticeably restricted, and lane changes require more care and vigilance on the part of the

driver. Minor incidents may be still absorbed, but the local deterioration in service will be substantial.

Queues may be expected to form behind any significant blockage.

LoS D is the level at which speeds begin to decline slightly with increasing flows and density begins to

increase somewhat more quickly. Freedom to maneuver within the traffic stream is more noticeably limited,

and the driver experiences reduced physical and psychological comfort levels. Every minor incident can be

expected to create queuing, because the traffic stream has little space to absorb disruptions.

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Page 2-3

Plate 2.1: Level of Service A

Plate 2.2: Level of Service B

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Page 2-4

Plate 2.3: Level of Service C

Plate 2.4: Level of Service D

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Page 2-5

Plate 2.5: Level of Service E

Plate 2.6: Level of Service F

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Page 2-6

At its highest density value, LoS E describes operation at capacity. Operations at this level are volatile,

because there are virtually no usable gaps in the traffic scene. Vehicles are closely spaced, leaving little

room to maneuver within the traffic stream at speeds that still exceed 80 Km/h. Any disruption of the traffic

stream, such as vehicles entering from a ramp or a vehicle changing lanes, can establish a disruption wave

that propagates throughout the upstream traffic flow. At capacity, the traffic stream has no ability to

dissipate even the most minor disruption, and any incident can be expected to produce a serious breakdownwith extensive queuing. Maneuverability within the traffic stream is extremely limited, and the level of

physical and psychological comfort afforded to the driver is poor.

LoS F describes breakdowns in vehicular flow. Such conditions generally exist within queues forming behind

breakdown points.

A suitably high Level of Service appropriate to each situation should be selected and used for design, and it

should be appreciated that for many of the hours of the day the road will in fact operate at a higher LoS.

Table 2.2 gives guidance for selecting appropriate Levels of Service in the design year for roads. It should

be noted that at intersections, the relevant LoS is normally one level lower than that shown.

Table 2.2: Guidelines for Selecting Level of Service in Kuwait

Road Class RuralUrban and

Suburban

Local D D

Collector C C

Arterial B C

Expressway or

FreewayB C

LoS is heavily dependent on the relationship between the demand (the predicted future design flow) and

the capacity of a road. These concepts properly lie outside the scope of a geometric design manual, and

have been introduced here to assist the designer to understand the work of the traffic engineer. In all cases

it is necessary for the highway designer and the traffic engineer to work closely together. The traffic

engineer will have the major input into elements where purely geometric considerations do not

predominate, in particular:

The prediction of future flows

The assessment of capacities and Levels of Service

The selection of appropriate service volumes

The design of weaving sections

The design of signalized and roundabout at-grade intersections (which depend on the results of detailed

traffic calculations)

The design of U-turn facilities

The primary measure of effectiveness for the Level of Service for differing types of facility will be assessed

in accordance with the criteria specified in the Highway Capacity Manual1, as given in Table 2.3.

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Page 2-7

Table 2.3: Primary Measures of Effectiveness for LoS Definition

Type of Facility Measure of Effectiveness

Expressways and Freeways:

Basic road segments Density

Weaving areas Speed

Merges and diverges Density

Arterial Roads Density

Collector Roads Speed

Local Roads Speed

Signalized intersections Average total delay

Un-signalized intersections Average total delay

Pedestrians Space, Delay

Source: Highway Capacity Manual

1

2.4 DESIGN VEHICLES

The entire range of the fleet of vehicles using Kuwaits roads has to be accommodated safely and

comfortably, and the standards set out in this manual respect this fact.

The operating characteristics of different vehicles influence the capacity of the road network. This is

reflected in the use of the Passenger Car Equivalent as a vehicle unit; larger and slower vehicles (which

physically cover more road space and take more room due to their slower acceleration capabilities and

greater braking needs) are counted as being equivalent to a number of passenger cars. Table 2.4 gives

broad equivalents for trucks and buses; for a more detailed assessment, the designer is referred to the

Highway Capacity Manual1.

Table 2.4: Passenger Car Equivalents of Trucks and Buses

Vehicle type Level terrain

Trucks 1.7

Buses 1.5

Recreational Vehicles 1.2

Source: Highway Capacity Manual1

The physical dimensions (including operating characteristics such as turning circles) are important in

determining lane widths, headroom, sight distances and turning radii. The design vehicles are identified in

Table 2.5. A check on typical vehicles in use on the roads in Kuwait confirms that the adoption of these

design vehicles is also appropriate to Kuwait.

2.5 PEDESTRIANS

Pedestrians need to be carefully considered when roads are being designed. They are present in every road

environment, unless specific measures are taken to provide for them outside the road corridor, for example

by means of fences and footbridges on motorways. Adequate provision for pedestrians should therefore be

made, using features such as sidewalks, pedestrian crossings, traffic signal facilities and grade separated

crossings, with curb details, ramps, bus stops etc being given special attention.

It is important to consider the type of pedestrian using the area. If near a school, for example, the designer

should have the young clearly in his mind, and therefore should provide more protection, better visibility

between driver and pedestrian, and enhanced signing, when compared to other areas.

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Page 2-8

Table 2.5: Design Vehicle Parameters

Description Code*Height

m

Width

m

Length

m

Min

Design

Turning

Radius

m

Min

Inside

Radius

m

Passenger Car P 1.3 2.1 5.8 7.3 4.4

Single Unit truck SU 3.4 4.1 2.4 9.2 12.8 8.6

Single Unit Bus BUS 3.2 2.6 12.2 12.8 8.0

Articulated Bus A-BUS 3.4 2.6 18.3 12.1 6.5

Intermediate Semi-Trailer WB-12 4.1 2.4 13.9 12.4 5.9

Intermediate Semi-Trailer WB-15 4.1 2.6 16.8 13.9 5.2

Inter-state Semi-Trailer WB-19 4.1 2.6 20.9 14.1 2.4

Inter-state Semi-Trailer WB-20 4.1 2.6 22.4 14.2 1.3

Triple Semi-Trailer / Trailers WB-30T 4.1 2.6 32.0 13.9 3.0

Turnpike Double Semi-trailer / Trailers WB-33D 4.1 2.6 34.8 18.4 4.5

Motor Home MH 3.7 2.4 9.2 12.7 7.9

Car & Camper Trailer P/T 3.1 2.4 14.8 13.1 5.3

Car & Boat Trailer P/B - 2.4 12.8 8.9 2.8

Motor Home and Boat Trailer MH/B 3.7 2.4 16.2 15.7 10.7

Source: AASHTO2

* Note that the designation WB relates to approximate wheelbase; WB-12 denotes a truck whose

wheelbase is around 12m.

Elderly people also require special consideration as they often move more slowly and may suffer from poor

sight and hearing deficiency. In locations where it is appropriate to design specifically for the needs of

elderly people, the following points should be borne in mind:

Assume lower walking speeds for the elderly and infirm

Provide wider refuge islands

Consider different surface textures at crossing points

Minimize crossing distances

Provide wider footpaths and sidewalks

Design for wheel chairs, for example by providing curb-cut ramps at crossing points

Provide paved footpaths and sidewalks

The width of sidewalk should accommodate the predicted pedestrian volumes. Table 2.6 shows the LoS

criteria to be adopted in the design of sidewalks. In the absence of pedestrian traffic forecasts, it isdesirable to provide a sidewalk of at least 3.0m width. Greater widths are probably necessary near

pedestrian generation sources such as schools, mosques, commercial areas or recreational areas such as

sports venues or cinemas.

In designing pedestrian facilities, an aim should be to provide routes that follow as closely as is practical,

the geographical desire lines for movement on foot. Where this would lead to haphazard, random or unsafe

crossings of traffic streams, it is appropriate to consider whether pedestrians can be channelled by guide

fences or other features to locations where purpose-designed safe crossings are to be provided.

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Part 1 Kuwait Highway Design Manual Design Speed

Page 3-3

3.7 INTERCHANGES

The ramps (or connecting roadways) within a grade-separated interchange should normally have a lower

design speed than the mainline.

Table 3.3 sets out the appropriate values.

Table 3.3: Minimum Design Speed for Connecting Roadways

Mainline

Design Speed

(km/h)

Minimum Design Speed for Connecting Roadways(km/h)

Free-flow Links Slips Loops

60 60 50 40

70 60 50 40

80 70 60 40

90 80 60 50

100 90 70 50

110 100 80 60

120 110 90 70

Source: AASHTO2

3.8 REDUCTION BELOW STANDARDS

In certain circumstances it may be uneconomic to design an alignment to the prescribed standards, and

consequently it may be necessary to reduce the standard of the road, perhaps only locally. As the

consequences of such reductions could be significant, the following guidance shall be taken as mandatory.

Having selected the relevant design speed for the length of route under consideration, this design speed

shall be maintained throughout, and not locally reduced.

At a site of particular difficulty, if a reduction from the value(s) prescribed for that design speed is

proposed, this shall only be permitted after receiving specific authorization from the Ministry of Public

Works, Kuwait Municipality and the Ministry of Interior.

____________________

1Kuwait Manual on Traffic Control Devices, 2011.

2A Policy on Geometric Design of Highways and Streets, AASHTO, 2004.

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Part 1 Kuwait Highway Design Manual Sight Distance

Page 4-1

4 SIGHT DISTANCE

4.1 GENERAL

In order to undertake a maneuver safely, a road user must have sufficient forward visibility. Three

situations in which forward visibility is particularly important are:

Stopping prior to reaching a stationary obstruction

Overtaking on an undivided road

Making a decision where a choice of actions presents itself

The corresponding distances for these three situations are:

Stopping Sight Distance (SSD)

Passing Sight Distance (PSD)

Decision Sight Distance (DSD)

The sight distance is always measured in a straight line between points on the centerline of each traffic

lane. On horizontal curves, the most critical lane is the nearest to the center of the curve.

In order to meet the required sight distance, roadside objects on the inside of a curve may need to be setback further from the edge of the travelled way than would be normal on a straight section of road. Further

details are given in Chapter 5.

4.2 EYE-HEIGHT AND OBJECT HEIGHT

For sight distance calculations for passenger vehicles, the height of the drivers eye is considered to be

1080mm above the ground surface. This value is based on a study found that average vehicle heights have

decreased to 1300mm with a comparable decrease in average eye heights to 1080mm. Because of various

factors that appear to place practical limits on further decreases in passenger car heights and the relatively

small increases in the lengths of vertical curves that would result from further changes that do occur,

1080mm is considered to be the appropriate height of drivers eye for measuring both stopping and passing

sight distances. For large trucks, the driver eye height ranges from 1800 to 2400mm. The recommended

value of truck driver eye height for design is 2330mm above the roadway surface1.

For stopping sight distance calculations, the height of object is considered to be 600mm above the roadsurface. For passing sight distance calculations, the height of object is considered to be 1080mm above the

road surface1.

The visibility envelope for sight distance is the area between the drivers eye-height and the object height.

The visibility envelope shall be checked in both the horizontal and vertical planes, between two points in the

center of the lane nearest to the center of the curve. On divided roads, both carriageways should be

checked.

4.3 STOPPING SIGHT DISTANCE (SSD)

Driver eye-height 1080mm

Object height 600mm

SSD is made up of two elements, namely perception-reaction distance and braking distance. Further

information on the formulae for calculating these elements can be found in AASTHO1.

The SSDs for design purposes are given in Table 4.1. Grade affects the breaking distance, and therefore

longer SSDs are required on downgrades. Upgrades shorten the breaking distance, but no change is made

to the SSD. The level values should be used for all upgrades.

4.4 PASSING SIGHT DISTANCE (PSD)

PSD applies to undivided two-way, two lane roads, in which a vehicle undertaking a passing maneuver

moves into the lane used by vehicles travelling in the opposite direction.

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Page 4-2


Object height 1080mm

Table 4.1: Stopping Sight Distance for Design

Design Speed(km/h)

Stopping Sight Distance (m)

Level & all

upgrades

Downgrade

2% 4% 6%

30 35 35 35 35

40 50 50 50 50

50 65 65 70 70

60 85 85 90 95

70 105 110 115 120

80 130 135 140 145

90 160 160 170 175

100 185 190 200 210

110 220 225 235 245

120 250 260 270 285

Source: AASHTO1

The PSD is the summation of four phases undertaken during a passing maneuver:

The initial maneuver

The occupation of the left lane

The clearance length

The opposing vehicle distance

Although grade does have an effect of PSD, no specific adjustments are to be made. However, designers

should be aware of the desirability of increasing the visibility beyond the minimum standard if passing is to

be accommodated on a length of road with significant grades.

The values of PSD for use in Kuwait are shown in Table 4.2.

Table 4.2: Passing Sight Distance for Design

Design Speed

(km/h)

Passing Sight Distance

(m)

30 200

40 270

50 345

60 410

70 485

80 540

90 615

100 670

Source: AASHTO1

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Page 4-3

4.5 DECISION SIGHT DISTANCE (DSD)

At certain points on the road network, a driver must make a decision as to which route to follow, or whether

there is a need to stop, and it is essential that adequate visibility is provided to allow the decision to be

made in suitable time. DSD to be provided at intersections is covered further in the relevant chapters later

in this manual.

The DSD is longer than the SSD as the correct course of action may be to stop and also because vehicles

cover significant distance when maneuvering without a reduction in speed.


Object height 600mm

DSD consists of the following elements:

Detection and recognition phase

Decision and response phase

Maneuver

DSD is measured from the vehicle location to the hazard (for example the Stop sign, the start of the bend

or the gore of the ramp terminal) and the values for varying design speeds are given in Table 4.3. There are

no adjustments required for grades.DSD should be provided where any of the following circumstances apply:

Unusual or unexpected maneuvers required at interchanges or intersections

Significant visual distractions, such as traffic control devices and illuminated advertisements

Changes in the road cross-section, such as a lane drop

Typical examples of such situations are:

A rural road leading directly to a STOP control

An urban road leading directly to a STOP control (sign or signals)

An off-ramp leading to an abrupt change in direction

The approach to a lane-drop or major fork

A complex weaving section (with more than two entries and exits)

It may not always be possible to provide full DSD and in these situations consideration should be

given to increasing the normal warning sign provision.

Table 4.3: Decision Sight Distance for Design

Design Speed

(km/h)

Decision Sight Distance

To Stop Control All Other Maneuvers

Rural Urban Rural Urban

50 70 155 145 195

60 95 195 170 235

70 115 235 200 275

80 140 280 230 315

90 170 325 270 360

100 200 370 315 400

110 235 420 330 430

120 265 470 360 470

Source: AASHTO1

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Page 4-4

4.6 MAINTAINING SIGHT DISTANCES

Sight distances should be checked at the design stage by direct measurement from a plan to 1:1250 scale

or larger. Care should be taken to ensure that no substantial objects obstruct the sightlines, including traffic

signs, barriers and bridge parapets. However, isolated slim objects such as lighting columns, sign supports

and individual tree trunks can be ignored.

On existing roads, sight distances are measured directly on the ground, by observation from the relevant

eye-height to a target at object height, along the centerline of each lane.

SSD should be maintained throughout the length of the route under consideration, and this may well have a

constraining influence on the design of other geometric elements of the road. DSD should be provided

under the circumstances described in Section 4.5.

On horizontal curves, it is necessary for obstructions to vision that are located on the inside of the curve to

be adequately set back from the edge of the travelled way. In particular, appropriate setbacks should be

provided to the face of barriers and bridge parapets located on the inside of the curve, and verge or median

widening may be necessary to accomplish this.

In cuttings, the side-slopes may interfere with forward visibility, and sight distances should be checked

three-dimensionally.

On vertical crest curves, the minimum values of curvature set out in Chapter 6 of this manual are adequateto cater for SSD, but it is always necessary to check to DSD, where relevant.

On vertical sag curves, the upper bound of the sight distance envelope should be checked where there is an

overhead obstruction to visibility such as an over-bridge or a sign gantry.

4.7 PROVISION OF PASSING SIGHT DISTANCE

It is not necessary for passing to be possible throughout the length of a two-way undivided road, but

frustration and unsafe maneuvers can result if there are insufficient opportunities provided to allow vehicles

to pass each other safely. As a minimum, half the route length should permit safe passing. Where this

cannot be achieved, consideration should be given to the provision of an auxiliary lane.

____________________

1 A Policy on Geometric Design of Highways and Streets, AASHTO, 2004.

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Part 1 Kuwait Highway Design Manual Horizontal Alignment

Page 5-1

5 HORIZONTAL ALIGNMENT

5.1 GENERAL

Road users should be able to travel along a roadway safely at a continuous uniform design speed, and the

horizontal alignment must be designed to permit this.Factors that influence the degree of horizontal curvature of a road include:

Safety

Design speed

Topography, adjacent land use and obstructions

Vertical alignment

Maximum allowable superelevation

Road classification

Cost

All of these factors must be balanced to produce a good alignment. Poor design will lead to a reduction in

the safety and capacity of the road.

In addition to the specific guidance given in this section, there are a number of general considerations thatare important in designing a safe and economic design. They are particularly applicable to high speed

situations and are listed below.

It is preferable to use a curve of greater radius than the minimum value quoted, retaining the use of minima

to more critical locations.

Compound circular curves, which consist of two or more arcs joined end-to-end in one direction, should be

used with caution and should be avoided where conditions permit the use of a simple curve. Where

compound curves are used, the radius of the flatter curve should not be more than 50 percent greater than

the radius of the sharper curve. This consideration however does not necessarily apply at intersections and

roundabouts, where lower speeds pertain.

Reverse circular curves, which consist of two arcs curving in opposite directions, on high speed roads

should include an intervening transition section of sufficient length to accommodate the reversal of

superelevation between the circular curves. If there is a length of normal crown tangent between the

curves, then the distance between reverse curves should be sufficient to accommodate the superelevationrunoff and the tangent runout for both curves. Where the superelevation is to be reversed without an

intervening normal crown section, the length between the reverse curves should be such that the

superelevation runoff lengths abut, thus providing only an instantaneous level section across the pavement.

Further details can be found in Section 5.4.4 of this manual.

Broken-back curves, which consist of two curves in the same direction connected with a short tangent,

should not be used. They are not expected by drivers and are not pleasing in appearance.

Horizontal alignment should be consistent with other design features and topography. In particular there is a

need for co-ordination with vertical alignment, and this is discussed in Chapter 6 of this manual.

On divided roads, consideration may be given to providing independent horizontal and vertical alignments

for each carriageway.

5.2 MAXIMUM SUPER ELEVATION

On a straight length of road, transverse drainage is accomplished by the use of crossfall at a standard rate

of 2%. On an undivided road, the surface normally falls outwards from both sides of a central crown line

(this arrangement being called normal crown), while on a divided road the surface of each pavement

normally falls outwards from the median.

On horizontal curves, this crossfall makes it more difficult for drivers on the outside of the curve to make

the turning maneuver, and so at radii below a certain value, it is necessary to eliminate this adverse

crossfall by making the whole road fall towards the inside edge of the curve. The resulting superelevation is

2%.

On tighter curves, a higher superelevation value can be adopted to assist drivers in travelling around the

corner.

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Page 5-2

The maximum superelevation is governed by the speed of the slower vehicles, whose drivers find it both

unexpected and difficult to have to exert a steering force against the direction of the curve. In Kuwait, rain

following a long dry period can result in low road surface friction factors, and therefore the use of relatively

steep cross falls is to be avoided.

The maximum superelevation to be used in Kuwait is shown in Table 5.1.

Table 5.1: Maximum Superelevation

Road ClassMaximum Superelevation (%)

Rural Urban

Local Road 4% 2%

Collector Road 6% 4%

Arterial Road 8% 6%

Expressways and Freeways 6% 6%

Loops (within interchanges) 8% 8%

5.3 MINIMUM CURVATURE

There is a direct relationship between the speed of a vehicle, the radius of the curve, the superelevation

and the side friction between the tire and the road surface.

R = V2

127(e+fs)

where R = radius of curve (m)

V = vehicle speed (km/h)

e = superelevation (%) divided by 100

fs= side friction factor

The side friction factor has been found from observations to lie in the range 0.35 to 0.50 on dry roads, but

on wet surfaces it may drop to around 0.20. On the grounds of safety, it is normal to adopt even lower

values for design purposes. Table 5.2 shows the values to be adopted.

Table 5.2: Side Friction Factors for Design

Design Speed Side Friction Factor

20 0.35

30 0.28

40 0.23

50 0.19

60 0.17

70 0.15

80 0.14

90 0.13

100 0.12

110 0.11

120 0.09

Source: AASHTO1

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Page 5-3

Accordingly, for a given design speed, minimum radii can be determined for a range of superelevation

rates, and these are given in Tables 5.3 through 5.5.

Table 5.3: Minimum Radii for Design Superelevation Rates, Design Speeds and emax = 4%

e (%)

Design Speed (km/h)

20 30 40 50 60 70 80 90 100

Minimum Radius (m)

NC 163 371 679 951 1310 1740 2170 2640 3250

2 102 237 441 632 877 1180 1490 1830 2260

2.5 45 116 241 390 567 793 1027 1295 1620

3 24 64 137 236 356 516 690 893 1150

3.5 15 42 89 157 241 356 483 636 778

4 8 22 47 86 135 203 280 375 492

Source: AASHTO1


e (%)

Design Speed (km/h)

20 30 40 50 60 70 80 90 100 110 120

Minimum Radius (m)

NC 194 421 738 1050 1440 1910 2360 2880 3510 4060 4770

2 138 299 525 750 1030 1380 1710 2090 2560 2970 3510

2.5 103 224 394 570 786 1055 1320 1620 1985 2315 2750

3 78 170 300 443 615 831 1050 1290 1590 1870 2240

3.5 56 132 223 347 488 669 848 1060 1310 1545 1875

4 36 156 155 261 380 635 690 870 1090 1300 1590

4.5 26 60 115 200 297 427 561 719 906 1105 1370

5 19 45 88 156 235 343 457 594 755 933 1190

5.5 14 34 67 122 185 274 359 485 621 779 1020

6 8 21 43 79 123 184 252 336 437 560 756

Source: AASHTO1

On local residential streets with design speeds of 70km/h and less, the use of superelevation for horizontal

curves can be minimized.

Although superelevation is advantageous for traffic operations, several factors combine to make its useimpractical for low-speed urban roads. These factors include:

Wide Pavement areas

The need to meet grades of adjacent property

Surface drainage considerations

The desire to maintain low-speed operations, and

Frequency of intersecting roads or driveways.

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Page 5-4


e (%)

Design Speed (km/h)

20 30 40 50 60 70 80 90 100 110 120

Minimum Radius (m)

NC 184 443 784 1090 1490 1970 2440 2970 3630 4180 4900

2 133 322 571 791 1090 1450 1790 2190 2680 3090 3640

2.5 102 249 442 616 847 1135 1410 1725 2110 2445 2885

3 81 199 354 496 684 916 1150 1410 1730 2000 2370

3.5 65 163 291 410 568 764 956 1180 1455 1690 2015

4 52 134 241 344 479 648 813 1010 1240 1450 1740

4.5 42 111 200 291 408 557 702 871 1080 1270 1530

5 30 87 163 246 349 480 611 762 947 1120 1360

5.5 23 68 131 206 298 417 535 673 839 998 1225

6 19 55 106 172 253 360 469 595 746 894 1100

6.5 16 45 88 146 216 313 411 527 665 806 1001

7 13 37 73 123 185 270 358 464 591 724 914

7.5 11 30 60 103 156 229 307 402 515 539 823

8 7 20 41 73 113 168 229 304 394 501 667

Source: AASHTO1

Therefore, horizontal curves on low-speed urban streets are frequently designed without superelevation.

Table 5.6 shows radii for various superelevation rates for low-speed urban streets at various speeds.

At intersections other than roundabouts, the normal crown or superelevation of the main road should be

continued through the intersection, with the minor road longitudinal profile tying in to the main road cross-

sectional profile.

At roundabouts, different considerations apply, and these are dealt with in Chapter 15 of this manual.

5.4 TRANSITION CURVES

5.4.1 General

Drivers naturally follow a transitional path as they change from a straight to a circular curve and good

highway design reflects this fact. The introduction of transition curves also improves the appearance of the

alignment and assists in the introduction of superelevation prior to the circular curve.

There are a number of transition curve types available to the designer and the use of the Euler spiral (or

clothoid), rather than other types such as the cubic parabola, is prescribed for Kuwait. In the spiral or

clothoid, the degree of curvature varies directly with the length along the curve.

Transitions are not required with circular curves whose radii are equal to or greater than those given in

Table 5.7. They are also not required on roads with design speeds of 70km/h or less.

Figure 5.1 shows the layout of a typical transition curve joining a straight (tangent) alignment to a circular

curve.

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Page 5-5

Table 5.6: Minimum Radii and Superelevation for Low-Speed Urban Streets ( 70 km/h)

e (%)

Design Speed (km/h)

20 30 40 50 60 70

Minimum Radius (m)

-6.0 11 32 74 151 258 429

-5.0 10 31 70 141 236 386

-4.0 10 30 66 131 218 351

-3.0 10 28 63 123 202 322

-2.5 10 28 62 120 196 309

-2.0 10 27 60 116 189 297

-1.5 9 27 59 113 183 286

0 9 25 55 104 167 257

1.5 9 24 51 96 153 234

2.0 9 24 50 94 149 227

2.5 8 23 50 92 146 221

3.0 8 23 48 89 142 214

3.5 8 23 48 88 139 210

4.0 8 22 47 86 135 203

4.5 8 22 46 84 132 198

5.0 8 21 45 82 129 193

5.5 8 21 44 81 126 188

6.0 8 21 43 79 123 184

Source: AASHTO1

Figure 5.1: Typical Arrangement of Transition Curve

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Page 5-6

Table 5.7: Maximum Radius for Use of a Spiral Curve Transition

Design Speed

(km/h)

Maximum Radius

(m)

30 55

40 95

50 150

60 215

70 290

80 380

90 480

100 595

110 720

120 855

Source: AASHTO1

5.4.2 Length of Transition Curve

The length of the transition curve (TS to SC on Figure 5.1) depends on the radius of the circular curve into

which it leads. It is defined by the following formula:

L = V3

46.7 x q x R

Where L = length of spiral (m)

V = design speed (km/h)

Q = rate of change of lateral acceleration (m/s3)

R = radius of circular curve (m)

The value of q is primarily dictated by comfort and safety considerations. A value of 0.3 m/s3to 1.2 m/s

3is

recommended. The minimum length of spiral is based on driver comfort and lateral shift, using a 1.2 m/s3

as a maximum rate of change in lateral acceleration.

The maximum transition length is limited to , where R is the radius of the circular curve. The designer

should ensure that the transition length used is below this value.

The desirable length of spiral is that which is approximately equal to the length of the natural spiral path

adopted by drivers. Differences between these two lengths results large lateral velocities or shifts in lateral

position at the end of the transition curve. A large lateral velocity in an outward direction (relative to the

curve) requires the driver to make a corrective steering maneuver that results in a path radius sharper than

the radius of the circular curve.

Such a critical radius produces an undesirable increase in peak side friction demand. Moreover, lateral

velocities of sufficient magnitude to shift a vehicle into an adjacent lane (without corrective steering) are

also undesirable for safety reasons1.

Table 5.8 depicts these desirable spiral lengths, which correspond to 2.0 s of travel time at the design

speed.

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Page 5-7

Table 5.8: Desirable Length of Spiral Curve Transition

Design Speed(km/h)

Desirable

Spiral Length

(m)

30 17

40 22

50 28

60 33

70 39

80 44

90 50

100 56

110 61

120 67

Source: AASHTO1

5.4.3 Length of Superelevation Application

The superelevation transition section comprises the superelevation runoff and tangent runout sections. The

superelevation runoff consists of the length of roadway needed to accomplish a change in outside-lane

cross slope from zero (flat) to full superelevation, or vice versa. The tangent runout section consists of the

length of roadway needed to accomplish a change in outside-lane cross slope from normal cross slope rate

to zero (flat), or vice versa.

The minimum length of superelevation runoff should be determined as:

Lr= (n1bw) w * ed

Where Lr = minimum length of superelevation runoff, m

n1 = number of lanes rotated

bw = adjustment factor for number of lanes rotated (see Table 5.9)

w = width of one traffic lane, m (typically 3.6m)

ed = design superelevation rate, percent

= maximum relative gradient, percent (see Table 5.10)

Table 5.11 includes typical minimum superelevation runoff lengths.

The minimum length of tangent runout should be determined as:

Lt= e

NCL

r

ed

Where Lt = minimum length of tangent runout, m

eNC = normal cross slope rate, percent

ed = design superelevation rate, percent

Lr = minimum length of superelevation runoff, m

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Page 5-8

Table 5.9: Adjustment Factor for Number of Lanes Rotated

Number of Lanes

Rotated

n1

Adjustment Factorbw

Runout Increase Relative

to One-Lane rotated

n1bw

1 1.00 1.0

1.5 0.93 1.25

2 0.75 1.5

2.5 0.70 1.75

3 0.67 2.0

3.5 0.64 2.25

Source: AASHTO1

Table 5.10: Maximum Relative Gradient

Design Speed(km/h)

Maximum Relative

Gradient

(%)

Equivalent MaximumRelative Slope

30 0.80 1:133

40 0.75 1:143

50 0.75 1:154

60 0.65 1:167

70 0.55 1:182

80 0.50 1:200

90 0.47 1:213

10 0.44 1:227

110 0.41 1:244

120 0.38 1:286

Source: AASHTO1

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Kuwait Bridges and Highway Structures Design Manual


Table 5.11: Superelevation Runoff Lr(m) for Horizontal Curves

e (%)

V = 20 km/h V = 40 km/h V = 60 km/h V = 80 km/h V = 100 k

Superelevation Runoff Lr(m) for Number of Lanes Rotated (1 typical for a 2-lane highway; 2 typical

1

Lr(m)

2

Lr(m)

3

Lr(m)

1

Lr(m)

2

Lr(m)

3

Lr(m)

1

Lr(m)

2

Lr(m)

3

Lr(m)

1

Lr(m)

2

Lr(m)

3

Lr(m)

1

Lr(m)

2

Lr(m)

NC 0 0 0 0 0 0 0 0 0 0 0 0 0 0

2.0 9 14 18 10 15 20 12 18 24 14 21 28 16 24

2.5 12 18 24 13 20 26 15 23 30 18 27 36 21 31

3.0 14 21 28 15 23 30 18 27 36 22 33 44 25 38

3.5 16 24 32 17 25 34 21 32 42 25 38 50 29 43

4.0 18 27 36 21 32 42 24 36 48 29 44 58 33 50

4.5 21 31 42 24 36 48 27 41 54 33 49 66 37 55

5.0 23 35 46 26 39 52 30 45 60 36 54 72 41 62

5.5 25 37 50 29 43 58 33 50 66 40 60 80 45 68

6.0 27 41 54 31 47 62 36 54 72 43 65 86 49 74

6.5 30 44 60 34 51 68 39 59 78 47 70 94 53 80

7.0 31 47 62 36 54 72 42 63 84 50 75 100 57 86

7.5 34 56 68 39 58 78 45 68 90 54 81 108 62 93

8.0 36 54 72 41 62 82 48 72 96 58 87 116 65 98

Source: AASHTO1

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Kuwait Bridges and Highway Structures Design Manual Chapter 5Part 1 Kuwait Highway Design Manual Horizontal Alignment

5.4.4 Application of Superelevation

Figure 5.2 shows typical methods of developing superelevation by rotating about the edges and about the

center of the road. The designer should use the most appropriate method to suit the situation. For divided

roads, greater consideration of topography, cut and fill, catchments and median drainage is required and

the designer should consider the possibility of adopting different vertical and/or horizontal geometry for thetwo separate pavements.

5.5 WIDENING ON CURVES

The rear wheels of vehicles do not exactly follow the track of the front wheels, and therefore it is necessary

to widen the pavement on low radius curves. It should be noted that widening is dependent on vehicle

geometry (particularly on wheelbase), lane width and curve radius.

Widening of turning roadways where the passing (one-way operation) or opposing (two-way operation)

traffic is of the same type is shown in Table 5.12. Typical application would be within industrial zones, at

approach ramps to seaports etc...

A more general application of widening of turning roadways is presented in Table 5.13.

It is good practice to provide all the additional pavement width by widening on the inside of the curve, as

shown on Figure 5.3. Widening is developed over the length of the transition, thus maintaining the fullwidening around the circular portion of the curve.

Figure 5.3: Application of Pavement Widening on Curves

5.6 SIGHT DISTANCE ON HORIZONTAL CURVES

The sight distance across the inside of horizontal curves is of special importance. Where there are sight

obstructions (such as walls, cut slopes, buildings and longitudinal barriers) on the inside of curves or the

inside of median lanes on divided highways, adjustment to the normal highway cross section may be

necessary if removal of the obstruction is impractical.

The following equation may be used to determine the HSO (horizontal sightline offset), the minimum

radius, or the available stopping sight distance, given the other two parameters:

HSO = R [1 cos 28.65 S]

R

Where HSO = horizontal sightline offset, m

R = radius of curve, m

S = stopping sight distance, m

Figure 5.4 shows components for determining the horizontal sight distance on curves.

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Table 5.12: Pavement Widths for Turning Roadways for Different Design Vehicles

Case I, One-Lane, One-Way OperationNo Provision for Passing a Stalled Vehicle

Radius on Inner Edgeof PavementR (m) P SU BUS-12 BUS-14 CITY-BUS S-BUS11 S-BUS12 A-BUS WB-12 WB-15

15 4.0 5.5 6.6 7.2 6.5 5.7 5.5 6.7 7.0 9.7

20 3.9 5.0 5.7 5.9 5.6 5.1 5.0 5.7 5.8 7.2

30 3.8 4.9 5.4 5.7 5.4 5.0 4.9 5.5 5.5 6.7

50 3.7 4.6 5.0 5.2 5.0 4.7 4.6 5.0 5.0 5.7

75 3.7 4.5 4.8 4.9 4.8 4.5 4.5 4.9 4.8 5.3

100 3.7 4.5 4.8 4.9 4.8 4.5 4.5 4.9 4.8 5.3

125 3.7 4.5 4.8 4.9 4.8 4.5 4.5 4.9 4.8 5.3

150 3.7 4.5 4.8 4.9 4.8 4.5 4.5 4.9 4.8 5.3

Tangent 3.6 4.2 4.4 4.4 4.4 4.2 4.2 4.4 4.2 4.4

Case II, One-Lane, One-Way OperationWith Provision for Passing a Stalled Vehicle by another of the Same Type

15 6.0 9.2 11.9 13.1 11.7 9.4 9.7 12.4 11.8 17.3

20 5.6 7.9 9.6 10.2 9.5 8.0 8.2 9.9 9.3 12.1

30 5.5 7.6 9.0 9.5 9.0 7.7 7.8 9.3 8.8 11.1

50 5.3 7.0 8.0 8.3 7.9 7.0 7.1 8.1 7.7 9.1

75 5.2 6.7 7.4 7.6 7.4 6.7 6.8 7.5 7.1 8.2

100 5.2 6.5 7.2 7.3 7.1 6.6 6.6 7.2 6.9 7.7

125 5.1 6.4 7.0 7.1 7.0 6.5 6.5 7.1 6.7 7.5

150 5.1 6.4 6.9 7.0 6.9 6.4 6.4 7.0 6.6 7.3

Tangent 5.0 6.1 6.4 6.4 6.4 6.1 6.1 6.4 6.1 6.4

Case III, Two-Lane, One-Way OperationWith Provision for Passing a Stalled Vehicle by another of the Same Type

15 7.8 11.0 13.7 14.9 13.5 11.2 11.5 14.2 13.6 19.1

20 7.4 9.7 11.4 12.0 11.3 9.8 10.0 11.7 11.1 13.9

30 7.3 9.4 10.8 11.3 10.8 9.5 9.6 11.1 10.6 12.9

50 7.1 8.8 9.8 10.1 9.7 8.8 8.9 9.9 9.5 10.9 75 7.0 8.5 9.2 9.4 9.2 8.5 8.6 9.3 8.9 10.0

100 7.0 8.3 9.0 9.1 8.9 8.4 8.4 9.0 8.7 9.5

125 6.9 8.2 8.8 8.9 8.8 8.3 8.3 8.9 8.5 9.3

150 6.9 8.2 8.7 8.8 8.7 8.2 8.2 8.8 8.4 9.1

Tangent 6.8 7.9 8.2 8.2 8.2 7.9 7.9 8.2 7.9 8.2

Source: AASHTO1

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Page 5-13

Table 5.13: Design Widths of Pavement for Turning Roadways

Radius oninner edge

of pavement,R (m)

Pavement Width( m)

Case I

One-lane, one-way

operation noprovision for passing

a stalled vehicle

Case II

One-lane, one-way

operation withprovision for passing

a stalled vehicle

Case IIITwo-lane operation

either one way or

two way

Design traffic conditions

A B C A B C A B C

15 5.4 5.5 7.0 6.0 7.8 9.2 9.4 11.0 13.6

25 4.8 5.0 5.8 5.6 6.9 7.9 8.6 9.7 11.1

30 4.5 4.9 5.5 5.5 6.7 7.6 8.4 9.4 10.6

50 4.2 4.6 5.0 5.3 6.3 7.0 7.9 8.8 9.5

75 3.9 4.5 4.8 5.2 6.1 6.7 7.7 8.5 8.9

100 3.9 4.5 4.8 5.2 5.9 6.5 7.6 8.3 8.7

125 3.9 4.5 4.8 5.1 5.9 6.4 7.6 8.2 8.5

150 3.6 4.5 4.5 5.1 5.8 6.4 7.5 8.2 8.4

Tangent 3.6 4.2 4.2 5.0 5.5 6.1 7.3 7.9 7.9

Width modification regarding edge treatment

No stabilized

shoulderNone None None

Sloping curb None None None

Vertical curb

one side Add 0.3m None Add 0.3m

two sides Add 0.6m Add 0.3m Add 0.6m

Stabilized shoulder,

one or bothsides

Lane width for Conditions

B &C on tangen

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