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Presentation about Delay
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Analysis of Signalized Intersections
2
What is Intersection analysis
Inverse application of the signal timing design In signal timing design, green times
are estimated to provide necessary capacity
In intersection analysis, signal timing is known and used to estimate the existing capacity
Two methods
Critical Movement Approach Apply adjustment factors to the
demand volume
HCM Methodology Saturation flow rates are reduced to
reflect non-ideal prevailing conditions
3
4
Steps for Critical Movement Approach
1. Identify the lane geometry and use 2. Identify hourly demand volumes 3. Specify the signal timing 4. Convert demand volumes to equivalent passenger-car
Volumes 5. Convert passenger-car equivalents to through-car
equivalents 6. Convert Through-car equivalents under prevailing
conditions to though-car equivalents under ideal conditions 7. Assign lane flow rates 8. Find critical-lane flows 9. Determine capacity and v/c ratios 10. Determine delay and level of service
5
1. Proportion of heavy vehicles 2. Proportion of local buses 3. Lane widths 4. Approach grade 5. Parking conditions on approach 6. Pedestrian interference levels
Identify hourly demand volumes
6
1. Proportion of heavy vehicles 2. Proportion of local buses 3. Lane widths 4. Approach grade 5. Parking conditions on approach 6. Pedestrian interference levels
Identify hourly demand volumes
Identify signal timings
7
1 2g G y ar l l= + + Effective green time Actual green time Actual yellow time Actual all-red time Start-up lost time Clearance lost time
gGy
ar1l2l
Convert Demand Volume to Equivalent Passenger Car Volume
8
(1 )pc HV HV LB LB HV LBV VP E VP E V P P= + +
Passenger-car Equivalents for Local Buses (Stop in Travel Lane)
9
Passenger-car Equivalents for Local Buses (Stop in Parking Lane)
10
Convert Passenger-Car Equivalent to Through-Car Equivalent
11
Left Turn Vehicles Protected left turns = 1.05 Permitted depends on opposing flow and
number of opposing lanes Right Turn Vehicles Depends on the pedestrian volume in
conflicting crosswalk
Through Car Equivalent for Left-Turning Vehicles
12
Through Car Equivalent for Right-Turning Vehicles
13
Though-car equivalents under ideal conditions
14
* * * *tcu
w g p LU
VvPHF f f f f
=
Adjustment factor for: Lane width Grade Parking Lane utilization
Lane Width Adjustment
15
Grade Adjustment
16
Parking Adjustment
17
Lane Utilization Adjustment
18
Assign Lane Flow Rates
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Where a separate LT lane exist, assign all LT tcus to this lane group. If more than one lane exists, divide the tcu/h equally among the lanes
Where a separate RT lane exist, assign all RT tcus to this lane group. If more than one lane exists, divide the tcu/h equally among the lanes
For all mixed lane group(LT/TH/RH, LT/TH, TH/RT)divide the total tcu/h equally among all lanes, except that all LT tcus must be in the LH lane and all RT tcus in RH lane
Find Critical Lane Flow Rates for Each Signal Phase
20
From A1 to A3 Ring 1 148+420=568 Ring 2 203+330=533
Maximum = 568
From B1 to B3 Ring 1 120+380=500 Ring 2 220+250=570
Maximum = 570 1138
Capacity and v/c Ratio
21
From A1 to A3 Ring 1 148+420=568 Ring 2 203+330=533
Maximum = 568
From B1 to B3 Ring 1 120+380=500 Ring 2 220+250=570
Maximum = 570 1138
1900( / )i ic g C=
11900( / )
n
SUM ii
c g C=
= /i i iX v c=
1/
n
c i ii
X v c=
=
Delay and Level of Service
22
1 2*i i id d PF d= +Approach delay for lane group i Uniform delay for lane group I Overflow plus random delay for lane group i Progression adjustment factor
id1id2id
PF
Uniform Delay and Overflow delay
23
2
10.5 [1 ( / )]
1 [min(1, )*( / )]i
ii i
C g CdX g C
=
22
16225[( 1) ( 1) ]ii i ii i
Xd X Xc N
= + +
Uniform Delay:
Overflow Delay:
Progression Factor
24
Level of Service
25
Example
26
Step 1 and 2: Geometry and volume
27
Step 3:Signal Phase
28
Step 4: Conversions to Equivalent Passenger Car Flow
29
EB Through movement 1100 veh/h, 10% heavy vehicle and 20 buses/hour Heavy=1100*10%*2.0=220 Bus=20*3.1=62 Passenger_car=1100*(1-10%)-20=970 Total=Heavy+Bus+Passenger_car=1252
Step 4: Conversions to Through-Car Equivalent
30
EB left turn Protected, equivalent=1.05
NB left turn One-way street, No conflicting through Go through pedestrian crosswalk Pedestrian volume 100 ped/h Treated like right turn, equivalent=1.21
Step 5: Conversions to Equivalent Under Ideal Condition
31
No parking, fp=1.0 EB lane width is 11 feet, fw=0.97 EB Through has two lanes f=0.952
Step 6: Assign Flow to Lanes
33
WB approach 183 tch/h for right turn and 1242 for
through Total 1424 uniformly split between two
lanes Leftmost lane 712 through only Rightmost lane carries 183 right turn and
1241-712=529 through
Step 6: Assign Flow to Lanes
34
Step 7: Critical Volume
35
Step 8: Capacity and v/c ratio
36
Step 8: Capacity and v/c ratio
37
Step 9: Delay and LOS
38
Uniform Delay:
Step 9: Delay and LOS
39
Overflow Delay:
Step 9: Delay and LOS
40
Total Delay = d1*PF+d2:
41
Steps for HCM Approach
1. Input data
2. Define movement groups and adjusted flow rate
3. compute lane group flow rate
4. input or compute phase duration
5. Compute capacity
6. Compute delays and LOS
42
43
Step 2: Movement and lane groups
44
Step 3: Estimating the Saturation Flow
Adjustment factors include: Lane width Heavy vehicles Grade Parking Local bus blockage Area type Pedestrian/bicycle interference
0 w HV g p bb a LU RT LT Rpb Lpbs s Nf f f f f f f f f f f=
45
Adjustment for Lane Width
Lanes width less than 10 ft Lane width between 10 and 12.9 ft Lane width larger than 12.9 ft
0.96wf =
1.0wf =
1.04wf =
46
Adjustment for Heavy Vehicles
Lanes width less than 10 ft Lane width between 10 and 12.9 ft Lane width larger than 12.9 ft
0.96wf =
1.0wf =
1.04wf =
47
Adjustment for Grade
1 / 200gf G=
G Grade in %
48
Adjustment for Parking
180.9 ( )3600
mNP = ( 1)pN Pf
N +
=
180.1 ( )3600 0.05
m
p
NNf
N
=
49
Adjustment for Local Bus Blockage
14.41.0 ( )3600
BNB = ( 1)bbN Bf
N +
=
14.4( )3600 0.05
B
p
NNf
N
=
50
Adjustment for Type of Area
0.9af =CBD location:
Other location: 1.0af =
51
Adjustment for Lane Utilization
1
gLU
g
vf
v N=
Demand flow rate for the lane group gv
1gv Demand flow rate for highest lane volume N Number of lanes in the lane group
52
Adjustment for Protected Turns
0.85RTf = For exclusive RT lane
0.95LTf = For protected LT lane
53
Adjustment for Pedestrian and Bicycle Interference with Turns
Estimate Pedestrian Flow Rate During Green Phase Estimate the Average Pedestrian Occupancy in the Conflict
Zone Estimate the Bicycle Flow Rate During the Green Phase Estimate the Average Bicycle Occupancy in the Conflict
Zone Estimate the Conflict Zone Occupancy Estimate the Unblocked Portion of the Phase Determine Adjustment Factors
54
Step 4: Determine Lane Group Capacities and v/c Ratios
Capacity of a lane group
v/c ratio of a lane group
Critical v/c ratio for intersection
( / )i i ic s g C=
( / )( / )
i ii
i i
v v sXc g C
= =
maxmin
max
( / ) *( )iC c
i
CX v sC L
=
55
Step 5: Critical Lane Group Identification
56
Step 6: Estimate Delay and LOS
Uniform Delay
Incremental Delay
Additional Delay Per Vehicle Due to Queue
1 2 3d d d d= + +
1d
2d
3d
57
Step 6: Estimate Delay and LOS
2
10.5 [1 ( / )]
1 [min(1, )*( / )]C g Cd
X g C
=
22
8900 [( 1) ( 1) ( )]kIXd T X XcT
= + + +
2 2 2
33600 ( )
2 2 2b e eo e eo bQ Q Q Q Q Qd t
vT c c+
= +
58
Step 6: Aggregate Delay
i ii
Ai
i
d vd
v=
A AA
IA
i
d vd
v=
59
Step 7: Interpret the Results
v/c ratios X for every lane group Critical v/c ratio X for the intersection Delays and LOS for each lane group Delays and LOS for each approach Delays for overall intersection
60
Step 7: Interpret the Results
Scenario I: Xc1.0, change of phase plan, cycle length, or physical design is needed
61
Example
62
Volume Adjustment
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Saturation Flow Rate Estimation
Saturation Flow Adjustment
64
Saturation Flow Adjustment
65
Saturation Flow Adjustment
66
Saturation Flow Adjustment
67
Saturation Flow Adjustment
68
Capacity Analysis
69
Delay and LOS
70
What is the result if applying HCM to the former Critical Movement analysis example?
71
72
1What is Intersection analysisTwo methodsSteps for Critical Movement Approach 5 6Identify signal timingsConvert Demand Volume to Equivalent Passenger Car VolumePassenger-car Equivalents for Local Buses (Stop in Travel Lane)Passenger-car Equivalents for Local Buses (Stop in Parking Lane)Convert Passenger-Car Equivalent to Through-Car EquivalentThrough Car Equivalent for Left-Turning VehiclesThrough Car Equivalent for Right-Turning VehiclesThough-car equivalents under ideal conditionsLane Width AdjustmentGrade AdjustmentParking AdjustmentLane Utilization AdjustmentAssign Lane Flow RatesFind Critical Lane Flow Rates for Each Signal PhaseCapacity and v/c RatioDelay and Level of ServiceUniform Delay and Overflow delayProgression FactorLevel of ServiceExampleStep 1 and 2: Geometry and volumeStep 3:Signal PhaseStep 4: Conversions to Equivalent Passenger Car FlowStep 4: Conversions to Through-Car EquivalentStep 5: Conversions to Equivalent Under Ideal Condition 32Step 6: Assign Flow to LanesStep 6: Assign Flow to LanesStep 7: Critical VolumeStep 8: Capacity and v/c ratioStep 8: Capacity and v/c ratioStep 9: Delay and LOSStep 9: Delay and LOSStep 9: Delay and LOSSteps for HCM Approach 42Step 2: Movement and lane groupsStep 3: Estimating the Saturation FlowAdjustment for Lane WidthAdjustment for Heavy VehiclesAdjustment for GradeAdjustment for ParkingAdjustment for Local Bus BlockageAdjustment for Type of AreaAdjustment for Lane UtilizationAdjustment for Protected TurnsAdjustment for Pedestrian and Bicycle Interference with TurnsStep 4: Determine Lane Group Capacities and v/c RatiosStep 5: Critical Lane Group IdentificationStep 6: Estimate Delay and LOSStep 6: Estimate Delay and LOSStep 6: Aggregate DelayStep 7: Interpret the ResultsStep 7: Interpret the ResultsExampleVolume AdjustmentSaturation Flow Rate EstimationSaturation Flow AdjustmentSaturation Flow AdjustmentSaturation Flow AdjustmentSaturation Flow AdjustmentSaturation Flow AdjustmentCapacity AnalysisDelay and LOS 71 72