Traffic Stream Characteristics

Report
TS4273 Traffic Engineering
UNSIGNALISED INTERSECTIONS
Scope 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 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 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
Unsignalised Intersections
•
•
•
•
Capacity (C)
Degree of saturation (DS)
Delay
Queue probability
Range of Variation in Empirical Data
for Input Variables (4-Arm)
Variable
Approach width (m)
Left-turn ratio
Right-turn ratio
Minor road flow ratio
Light vehicle-%
Heavy vehicle-%
Motorcycle-%
Unmotorised flow ratio
Min.
3,5
0,10
0,00
0,27
29
1
19
0,01
Avg.
5,4
0,17
0,13
0,38
56
3
33
0,08
Max.
9,1
0,29
0,26
0,50
75
7
67
0,22
Range of Variation in Empirical Data
for Input Variables (3-Arm)
Variable
Approach width (m)
Left-turn ratio
Right-turn ratio
Minor road flow ratio
Light vehicle-%
Heavy vehicle-%
Motorcycle-%
Unmotorised flow ratio
Min.
3,5
0,06
0,09
0,15
34
1
15
0,01
Avg.
4,9
0,26
0,29
0,29
56
5
32
0,07
Max.
7,0
0,50
0,51
0,41
78
10
54
0,25
Definition of Unsignalised
Intersection Types in IHCM (4-Arm)
Type Code
422
424
424M
444
444M
Minor road
Major road approaches
approaches
No. of lanes Median No. of lanes
1
N
1
2
N
1
2
Y
1
2
N
2
2
Y
2
Definition of Unsignalised
Intersection Types in IHCM (3-Arm)
Type Code
322
324
324M
344
344M
Minor road
Major road approaches
approaches
No. of lanes Median No. of lanes
1
N
1
2
N
1
2
Y
1
2
N
2
2
Y
2
STEP 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 Condition
•
•
•
•
•
Sketch of turning movement flow
Traffic composition
pcu-factor
K-factor
pce-values
STEP A-2: Traffic Condition
STEP 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 CS
[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 RE
[Table A-3:2 p.3-29]
Commercial
Residential
Restricted
Access
Commercial land use (e.g. shops,
restaurants, offices) with direct
roadside access for pedestrians
and vehicles
Residential land use with direct
roadside access for pedestrians
and vehicles
No or limited direct roadside
access (e.g. due to the existence
of physical barriers, frontage
streets etc).
Side 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
and Intersection Type
A
a
10m
D
d
B
10m
10m
10m
c
C
b
STEP B-1: Approach Width and
Intersection Type
A
Average intersection
approach width, WI:
WI = (a/2+b+c/2+d/2)/4
a
10m
D
d
If A is only exit:
B W = (b+c/2+d/2)/3
I
10m
10m
10m
c
C
b
Road entry widths:
WAC = (a/2+c/2)/2
WBD = (b+d/2)/2
STEP B-1: Approach Width and
Intersection Type
A
Average road approach
width WAC,WBD (m)
WBD = (b+d/2)/2 < 5,5
No. of lanes (total for both
directions)  2
a
10m
D
d
B
10m
10m
10m
c
C
b
WAC = (a/2+c/2)/2  5,5
No. of lanes (total for both
directions)  4
STEP B-1: Approach Width and
Intersection Type
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.
STEP B-1: Approach Width and
Intersection Type
IT Code
No. of
No. of
intersection minor road
arms
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 C0
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
Adjustment Factor FW
• 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-3: Approach Width
Adjustment Factor FW
• 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
Adjustment Factor FM
Description
Type M
Median
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
Factor FCS
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
Friction & Unmotorised AF FRSU
Road Environment Type, Side Friction and
Unmotorised Vehicles Adjustment Factor FRSU
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.00
0.05
0.10
0.15
0.20
Ratio of Unmotorised Vehicles pUM
CH
CM
CL
RH
RM
RL
RAHML
0.25
STEP B-7: Left-Turning
Adjustment Factor FLT
FLT  0,84  1,61pLT
STEP B-8: Right-Turning
Adjustment Factor FRT
• 4-arm
FRT  1,0
• 3-arm
FRT  1,09  0,922pRT
STEP B-9: Minor Road Flow Ratio
Adjustment Factor FMI
422 (pMI 0,1-0,9)
• FMI=1,19pMI2-1,19pMI+1,19
424 (pMI 0,1-0,3)
• FMI=16,6pMI4-33,3pMI3+25,3pMI2-8,6pMI+1,95
444 (pMI 0,3-0,9)
• FMI=1,11pMI2-1,11pMI+1,11
STEP B-9: Minor Road Flow Ratio
Adjustment Factor FMI
322 (pMI 0,1-0,5)
• FMI=1,19pMI2-1,19pMI+1,19
322 (pMI 0,5-0,9)
• FMI=-0,595pMI2+0,595pMI+0,74
342 (pMI 0,1-0,5)
• FMI=1,19pMI2-1,19pMI+1,19
342 (pMI 0,5-0,9)
• FMI=2,38pMI2-2,38pMI+1,49
STEP B-9: Minor Road Flow Ratio
Adjustment Factor FMI
324 (pMI 0,1-0,3)
• FMI=16,6pMI4-33,3pMI3+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 C
C  C0  FW  FM  FCS  FRSU  FLT  FRT  FMI
STEP C-1: Degree of Saturation DS
DS  Qtotal / C
STEP C-2: Delays D
(Intersection Traffic Delay DTI)
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
(Major Road Traffic Delay DTMA)
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
(Minor Road Traffic Delay DTMI)
• DTMI = (QTOTAL x DTI – QMA x DTMA) / QMI
STEP C-2: Delays D
(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
(Intersection Delay D)
• D = DG + DTI
STEP C-3: Queue Probability
QP(%)  47,71DS  24,68DS  56,47DS
2
QP(%)  9,02DS  20,66DS  10,49DS
2
3
3
STEP C-4: Evaluation of
Traffic 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)

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