UNSIGNALISED INTERSECTIONS TS4273 Traffic Engineering.

UNSIGNALISED INTERSECTIONSUNSIGNALISED INTERSECTIONS

TS4273 Traffic EngineeringTS4273 Traffic Engineering

Scope and ObjectivesScope and Objectives

This chapter deals with 3-arm and 4-arm unsignalised intersections which are formally controlled by the basic Indonesian traffic code rule give-way to the left.

This method assumes right angled intersections in flat alignment and is valid for degree of saturation less than 0,8-0,9.

Traffic Safety ConsiderationsTraffic Safety Considerations

• Effect of intersection layout– 3-arm with T-shape 40% lower accident

rates than 4-arm.– Y-shape have 15-50% higher accident rates

than T-shape.

• Effect of geometric design– Median (3-4m) on major road reduces the

accident rates (if the road wider than 10m)

Traffic Safety ConsiderationsTraffic Safety Considerations

• Effect of intersection control– Yield sign control reduces the accident rates

60% compare to priority from the left– Stop sign control reduces the accident rates

40% as compared to yield sign.– Traffic signal control reduces the accident

rates 20-50% compared to uncontrolled operation.

Performance Measures of Performance Measures of Unsignalised IntersectionsUnsignalised Intersections

• Capacity (C)

• Degree of saturation (DS)

• Delay

• Queue probability

Range of Variation in Empirical Data Range of Variation in Empirical Data for Input Variables (4-Arm)for Input Variables (4-Arm)

Variable Min. Avg. Max.

Approach width (m) 3,5 5,4 9,1

Left-turn ratio 0,10 0,17 0,29

Right-turn ratio 0,00 0,13 0,26

Minor road flow ratio 0,27 0,38 0,50

Light vehicle-% 29 56 75

Heavy vehicle-% 1 3 7

Motorcycle-% 19 33 67

Unmotorised flow ratio 0,01 0,08 0,22

Range of Variation in Empirical Data Range of Variation in Empirical Data for Input Variables (3-Arm)for Input Variables (3-Arm)

Variable Min. Avg. Max.

Approach width (m) 3,5 4,9 7,0

Left-turn ratio 0,06 0,26 0,50

Right-turn ratio 0,09 0,29 0,51

Minor road flow ratio 0,15 0,29 0,41

Light vehicle-% 34 56 78

Heavy vehicle-% 1 5 10

Motorcycle-% 15 32 54

Unmotorised flow ratio 0,01 0,07 0,25

Definition of Unsignalised Definition of Unsignalised Intersection Types in IHCM (4-Arm)Intersection Types in IHCM (4-Arm)

Type CodeMajor road approaches

Minor road approaches

No. of lanes Median No. of lanes

422 1 N 1

424 2 N 1

424M 2 Y 1

444 2 N 2

444M 2 Y 2

Definition of Unsignalised Definition of Unsignalised Intersection Types in IHCM (3-Arm)Intersection Types in IHCM (3-Arm)

Type CodeMajor road approaches

Minor road approaches

No. of lanes Median No. of lanes

322 1 N 1

324 2 N 1

324M 2 Y 1

344 2 N 2

344M 2 Y 2

STEP A-1: Geometric ConditionsSTEP A-1: Geometric Conditions

• Date• Handle by• City and province• Major and minor road names• Case• Period• Sketch of intersection geometry and

dimension

STEP A-2: Traffic ConditionSTEP A-2: Traffic Condition

• Sketch of turning movement flow

• Traffic composition

• pcu-factor

• K-factor

• pce-values

STEP A-2: Traffic ConditionSTEP A-2: Traffic Condition

STEP A-3: Environmental ConditionSTEP A-3: Environmental Condition

• City Size (p.3-29 Table A-3:1 or p.3-34 Table B-5:1)

• Road Environment (p.3-29 Table A-3:2 or p.3-35 Table B-6:1)

• Side Friction (p.3-29 Table A-3:2 or p.3-35 Table B-6:1)

City Size Classes CSCity Size Classes CS[Table A-3:1 p.3-29][Table A-3:1 p.3-29]

City Size Inhab. (M)

Very Small 0,1

Small > 0,1 - 0,5

Medium > 0,5 - 1,0

Large > 1,0 - 3,0

Very Large > 3,0

Road Environment Type RERoad Environment Type RE[Table A-3:2 p.3-29][Table A-3:2 p.3-29]

Commercial

Commercial land use (e.g. shops, restaurants, offices) with direct

roadside access for pedestrians and vehicles

ResidentialResidential land use with direct roadside access for pedestrians

and vehicles

Restricted Access

No or limited direct roadside access (e.g. due to the existence

of physical barriers, frontage streets etc).

Side Friction class SFSide Friction class SF

• Side friction describes the impact of road side activities in the intersection area on the traffic discharge, e.g. pedestrians walking on or crossing the carriageway, angkot and buses stopping to pick up or let off passengers, vehicle entering and leaving premises and parking lots outside the carriageway.

• Side friction is defined qualitatively from traffic engineering judgment as high, medium or low.

STEP B-1: Approach Width STEP B-1: Approach Width and Intersection Typeand Intersection Type

10m

10m

10m

10m

A

B

C

D

a

b

c

d

STEP B-1: Approach Width and STEP B-1: Approach Width and Intersection TypeIntersection Type

Average intersection approach width, WI:

WI = (a/2+b+c/2+d/2)/4

If A is only exit:

WI = (b+c/2+d/2)/3

Road entry widths:

WAC = (a/2+c/2)/2

WBD = (b+d/2)/2

10m

10m

10m

10m

A

B

C

D

a

b

c

d


Average road approach width WAC,WBD (m)

WBD = (b+d/2)/2 < 5,5

No. of lanes (total for both directions) 2

WAC = (a/2+c/2)/2 5,5

No. of lanes (total for both directions) 4

10m

10m

10m

10m

A

B

C

D

a

b

c

d


Average road approach widths WAC, WBD and Average intersection approach width WI.

• WAC = (WA+WC)/2 and WBD = (WB+WD)/2

• WI = (WA+WC+WB+WD)/no. intersection arms.


IT CodeNo. of

intersection arms

No. of minor road

lanes

No. of major road

lanes

322 3 2 2

324 3 2 4

342 3 4 2

422 4 2 2

424 4 2 4

STEP B-2: Base Capacity Value CSTEP B-2: Base Capacity Value C00

Intersection Type Base Capacity C0 (pcu/h)

322 2.700

342 2.900

324 or 344 3.200

422 2.900

424 or 444 3.400

STEP B-3: Approach Width STEP B-3: Approach Width Adjustment Factor FAdjustment Factor FWW

• 422 FW = 0,70 + 0,0866 WI

• 424 or 444 FW = 0,61 + 0,0740 WI

• 322 FW = 0,73 + 0,0760 WI

• 324 or 344 FW = 0,62 + 0,0646 WI

• 342 FW = 0,67 + 0,0698 WI

STEP B-4: Major Road Median STEP B-4: Major Road Median Adjustment Factor FAdjustment Factor FMM

Description Type MMedian

adjustment factor, FM

No major road median. None 1,00

Major road median exists, width < 3m

Narrow 1,05

Major road median exists, width 3m

Wide 1,20

STEP B-5: City Size Adjustment STEP B-5: City Size Adjustment Factor FFactor FCSCS

City Size Inhab. (M) FCS

Very Small 0,1 0,82

Small > 0,1 - 0,5 0,88

Medium > 0,5 - 1,0 0,94

Large > 1,0 - 3,0 1,00

Very Large > 3,0 1,05

STEP B-6: Road Environment, Side STEP B-6: Road Environment, Side Friction & Unmotorised AF FFriction & Unmotorised AF FRSURSU

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.00 0.05 0.10 0.15 0.20 0.25

Ratio of Unmotorised Vehicles pUM

Ro

ad

En

vir

on

me

nt

Typ

e, S

ide

Fri

cti

on

an

d

Un

mo

tori

se

d V

eh

icle

s A

dju

stm

en

t F

acto

r F

RS

U

CH CM CL RH RM RL RAHML

STEP B-7: Left-Turning STEP B-7: Left-Turning Adjustment Factor FAdjustment Factor FLTLT

LTLT pF 61,184,0

STEP B-8: Right-Turning STEP B-8: Right-Turning Adjustment Factor FAdjustment Factor FRTRT

• 4-arm

• 3-arm

0,1RTF

RTRT pF 922,009,1

STEP B-9: Minor Road Flow Ratio STEP B-9: Minor Road Flow Ratio Adjustment Factor FAdjustment Factor FMIMI

422 (pMI 0,1-0,9)

• FMI=1,19pMI2-1,19pMI+1,19

424 (pMI 0,1-0,3)

• FMI=16,6pMI4-33,3pMI

3+25,3pMI2-8,6pMI+1,95

444 (pMI 0,3-0,9)

• FMI=1,11pMI2-1,11pMI+1,11


322 (pMI 0,1-0,5)• FMI=1,19pMI

2-1,19pMI+1,19

322 (pMI 0,5-0,9)• FMI=-0,595pMI

2+0,595pMI+0,74

342 (pMI 0,1-0,5)• FMI=1,19pMI

2-1,19pMI+1,19

342 (pMI 0,5-0,9)• FMI=2,38pMI

2-2,38pMI+1,49


324 (pMI 0,1-0,3)

• FMI=16,6pMI4-33,3pMI

3+25,3pMI2-8,6pMI+1,95

344 (pMI 0,3-0,5)

• FMI=1,11pMI2-1,11pMI+1,11

344 (pMI 0,5-0,9)

• FMI=-0,555pMI2+0,555pMI+0,69

STEP B-10: Actual Capacity CSTEP B-10: Actual Capacity C

MIRTLTRSUCSMW FFFFFFFCC 0

STEP C-1: Degree of Saturation DSSTEP C-1: Degree of Saturation DS

CQtotalDS /

STEP C-2: Delays D STEP C-2: Delays D (Intersection Traffic Delay DT(Intersection Traffic Delay DTII))

DS 0,60

• DTI = 2 + 8,2078DS - (1-DS)2

DS > 0,60

• DTI = [1,0504/(0,2742-0,2042DS)] - (1-DS)2

STEP C-2: Delays D STEP C-2: Delays D (Major Road Traffic Delay DT(Major Road Traffic Delay DTMAMA))

DS 0,60

• DTMA = 1,8 + 5,8234DS - (1-DS) 1,8

DS > 0,60

• DTMA = [1,05034/(0,346-0,246DS)] - (1-DS) 1,8

STEP C-2: Delays D STEP C-2: Delays D (Minor Road Traffic Delay DT(Minor Road Traffic Delay DTMIMI))

• DTMI = (QTOTAL x DTI – QMA x DTMA) / QMI

STEP C-2: Delays D STEP C-2: Delays D (Intersection Geometric Delay DG)(Intersection Geometric Delay DG)

• DS < 1,00

• DG = (1-DS) x (pTx6 + (1-pT)x3) + 4xDS

• DS 1,00• DG = 4

STEP C-2: Delays D STEP C-2: Delays D (Intersection Delay D)(Intersection Delay D)

• D = DG + DTI

STEP C-3: Queue ProbabilitySTEP C-3: Queue Probability

32 47,5668,2471,47(%) DSDSDSQP

32 49,1066,2002,9(%) DSDSDSQP

STEP C-4: Evaluation of STEP C-4: Evaluation of Traffic PerformanceTraffic Performance

• If the obtain DS values are too high (> 0,75), we should revise our assumptions regarding approach width etc and make a new set of calculations.

Perbaikan Simpang Tak Bersinyal di Indonesia

• Perbaikan geometri (sudut & radius tikungan)

• Manajemen lalulintas (rambu & marka)

• Pengaturan PKL (represif & preventif)

• Pulau lalulintas (lebar jalan > 10 m)

• Lebar median di jalan utama (min 3-4 m)

UNSIGNALISED INTERSECTIONS TS4273 Traffic Engineering.

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