Adaptive Traffic Signal Control - West Virginia Department...
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Adaptive Traffic Signal Control WVDOH/MPO/FHWA Planning Conference 10/3/2012 Andrew P. Nichols, PhD, PE Rahall Transportation Institute
Transcript of Adaptive Traffic Signal Control - West Virginia Department...
Adaptive Traffic Signal Control WVDOH/MPO/FHWA Planning Conference 10/3/2012
Andrew P. Nichols, PhD, PE Rahall Transportation Institute
Presentation Overview Traffic Signals 101 Types of Traffic Signal Control Terminology Overview
What is Adaptive Signal Control? Adaptive Systems in WV Preliminary Evaluation Results Simulation Field Data
Planning for Traffic Signals
Types of Traffic Signal Control Basic (Free) Operation With or without vehicle/pedestrian detection Commonly used for isolated intersections Green times programmed based on anticipated demand
Coordinated (Time-of-Day) Operation With or without vehicle/pedestrian detection Used in corridor or downtown grid signal systems Cycle, Offset, and Splits are the key parameters that are typically
programmed for anticipated demand at different time periods Adaptive Operation Requires vehicle detection Most systems dynamically adjust Cycle, Offset, and Splits based on
current or historical demand
What is a Phase Split? Each signalized intersection movement is a phase 4-way intersection with left-turn arrows has 8 phases Split Time = Green + Yellow + All Red
1
5 2 2
1 6 6 7 4 4
3 8
8
2 3 4
5 6 7 8
Phase Movement
What is a Phase Split? Phase split times are programmed to account for demand Duration can also be shortened with vehicle detection
1 2 3 4
5 6 7 8
Phase 8 Split = G + Y + R
What is a Cycle? The total time it takes to serve all phase splits
1 2 3 4
5 6 7 8
Cycle = Split 1 + Split 2 + Split 3 + Split 4 Cycle = Split 5 + Split 6 + Split 7 + Split 8
What is an Offset? Programmed for the “mainline” movement at each
intersection to provide progression through the system i.e., Offsetting the start of green
Consider a Northbound Phase 2 movement only:
1 2 3 4
5 6 7 8
1 2 3 4
Time-Space Diagram (NB)
Spac
e (f
eet)
Time (seconds)
1
2
3
8:00:00
1 2 3 4 1 2 3 4 1
1 2 3 4 1 2 3 4 1
1 2 3 4 1 2 3 4 1
Time-Space Diagram (Zero Offset)
Time (seconds)
1
2
3
8:00:00
2 2
2 2
2 2
Vehicle Trajectory
Spac
e (f
eet)
Time-Space Diagram (w/ offsets)
Time (seconds)
1
2
3
8:00:00
2 2
2 2
2 2
Vehicle Trajectory
Spac
e (f
eet)
Offset 1
Offset 2
Time-Space Diagram (w/ offsets)
Time (seconds)
1
2
3
8:00:00
2 2
2 2
2 2
Spac
e (f
eet)
Offset 1
Offset 2
Coordination Plans Traffic engineers can deploy multiple coordination plans
to accommodate different traffic patterns How are these plans derived?
This process cannot account for all traffic patterns!
Traffic Data Collection Optimization Software Field Tuning
Saturday 2
Star City Bridge, Morgantown Inbound Traffic on Saturday When to start each Coordination Plan?
Plan 2 Plan 3 Plan 1 Plan 2 Plan 3 Plan 1
Oops!
Saturday 1
Star City Bridge, Morgantown Saturday Traffic Should offsets
provide progression for INBOUND or OUTBOUND traffic?
Inbound
Saturday 1
Outbound
Favor Outbound!
Inbound
Saturday 2
Outbound
Oops!
What is Adaptive Signal Control? Respond more intelligently to fluctuations in traffic
patterns (beyond shortening phase times with vehicle detection)
All adaptive systems require vehicle detection Adjust phase split times More/less time for a left-turn movements or side streets
Adjust cycle length Longer for congested periods, shorter for off-peak
Adjust offsets Accommodate inbound vs. outbound traffic Account for change in traffic speeds due to severe weather
Adaptive Signal Control 20+ adaptive control systems on the market <1% of signals nationwide use adaptive technology NONE of the systems are “plug and play” Each system is unique
FHWA Every Day Counts Initiative Identified ASC as being significantly underutilized Providing some guidance on how to select a system Developing guidelines on how to evaluate performance
Adaptive Systems in WV WVDOH operates traffic signals statewide ~1,900 traffic signals ~107 closed loop signal systems (running coordinated timings)
Adaptive Signal Control Deployments (16) Morgantown WV-705 Corridor (In Progress) (5) Teays Valley SR-34 Corridor (Summer 2012) (3) Elkins US-219 Corridor (In Progress) (5) St. Albans US-60 Corridor (In Progress) (8) Morgantown Beechurst/University Corridor (Spring 2013)
Rahall Transportation Institute is managing and evaluating the performance of these systems
Adaptive Signal Control Evaluation Morgantown WV-705 Corridor Adaptive System: ACS-Lite & Traffic Responsive Hybrid Evaluation Mechanism
Intersection Delay & Progression – Simulation using VISSIM Travel Time – Bluetooth & GPS Safety – Eventually crash records
Teays Valley SR-34 Corridor Adaptive System: InSync Evaluation Mechanism
Travel Time – GPS
WV 705 Signalized Intersections
16 Mainline Signals
~5.2 miles end-to-end Stopbar detection Advanced detection
WV 705 Traffic Generators
WVU Football
WVU Basketball
Shopping Mall
Shopping Mall
CBD
Downtown Campus
Engineering Campus
Student Housing
Hospitals
School
School
Research Park
Residential
New Housing
Commuters
WV 705 Corridor
WV 705 System Evaluation with Simulation WV 705 corridor was modeled in VISSIM with traffic
signal controller simulators to evaluate: Free operation (no coordination) Basic Coordination Plans (TOD) TOD + Traffic Responsive (TR) TOD + ACS-Lite (ACS) TOD + TR + ACS (Adaptive)
Total Delay and Hourly Delay Summarized By System (All intersection movements) By Mainline Movement (705 thru movements) By Minor Movement (Left-turns and side-streets)
22 2 2 233 3 3 344 4 4 4
6
6 6 6 67
7 77 79
9 99 9
0
500
1000
1500
2000
2500
3000
Free TOD TOD+ACS TR TR+ACS
Tota
l Del
ay (v
eh-h
/h)
1880
2556 25262262 2236
2 2 2 2 23 3 3 3 3
4 4 4 4 4
66 6 6 6
7
7 7 7 7
9
9 9 9 9
0
200
400
600
800
1000
1200
Free TOD TOD+ACS TR TR+ACS
Tota
l Del
ay (v
eh-h
/h)
1021
808 813 820 812
22 2 2 23
3 33 34
4 44 46
6 66 6
7
7 77 7
9
9 99 9
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Free TOD TOD+ACS TR TR+ACS
Tota
l Del
ay (v
eh-h
/h)
859
1748 1714
1442 1424
All Movements
Major Movements
Minor Movements
System Delay is lowest in Free, but major movements suffer
All Movements
Major Movements
Minor Movements
0102030405060708090
100
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:0
010
:30
11:0
011
:30
12:0
012
:30
13:0
013
:30
14:0
014
:30
15:0
015
:30
16:0
016
:30
17:0
017
:30
18:0
018
:30
Tota
l Del
ay (v
eh-h
)
Time of Day
FREE
TOD
TOD+ACS
TR
TR+ACS
0
5
10
15
20
25
30
35
40
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:0
010
:30
11:0
011
:30
12:0
012
:30
13:0
013
:30
14:0
014
:30
15:0
015
:30
16:0
016
:30
17:0
017
:30
18:0
018
:30
Tota
l Del
ay (v
eh-h
)
Time of Day
FREE
TOD
TOD+ACS
TR
TR+ACS
0
10
20
30
40
50
60
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:0
010
:30
11:0
011
:30
12:0
012
:30
13:0
013
:30
14:0
014
:30
15:0
015
:30
16:0
016
:30
17:0
017
:30
18:0
018
:30
Tota
l Del
ay (v
eh-h
)
Time of Day
FREE
TOD
TOD+ACS
TR
TR+ACS
Major Movements suffer
in “free” mode
Adaptive provides most benefit over
TOD during off-peak
0
18
36
54
72
90
0
18
36
54
72
90
0
8
16
24
32
40
0
8
16
24
32
40
0
8
16
24
32
40
0
8
16
24
32
40
0
8
16
24
32
40
0
8
16
24
32
40
Cumulative Total Delay – University & Patteson
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Time of Day
Cum
ulat
ive
Tota
l Del
ay (
veh-
h)
5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00
5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00 5:30 10:00 14:00 19:00
Φ5: Eastbound Left Φ6: Westbound Φ7: Southbound Left Φ8: Northbound
Φ1: Westbound Left Φ2: Eastbound Φ3: Northbound Left Φ4: Southbound
Adaptive Off Adaptive On
Left-Turn Delay Decreased by Shifting Available Green Time
Coordination Diagram to Evaluate Offsets
End of Phase
Start of Phase
Vehicle Arrivals
GOOD Vehicles arrive
after green
BAD Vehicles arrive before green
Cyc
le T
ime
Time-of-Day
Offset Adjustment Willowdale – Suncrest Town Center
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 3600 7200 10800 14400 18000 21600 25200 28800 32400 36000 39600 43200 46800 50400 54000
Cum
ulat
ive
Arriv
als
on G
reen
Simulation Time
ACS-Lite OFF ACS-Lite ON
Teays Valley WV-34 System Overview
5 Mainline Signals
Northbound - GPS Travel Time Weekday 7AM–11AM
Average (seconds)
Std Dev (seconds)
35 mph Baseline 66 -- Before 175 39 After 110 29 % Change -37% --
Before After
Dis
tanc
e A
long
Cor
rido
r (m
iles)
Travel Time (seconds)
Northbound - GPS Travel Time Weekday 11AM–2PM
Average (seconds)
Std Dev (seconds)
35 mph Baseline 66 -- Before 165 33 After 98 29 % Change -41% --
Before After
Dis
tanc
e A
long
Cor
rido
r (m
iles)
Travel Time (seconds)
Northbound - GPS Travel Time Weekday 2PM–6PM
Average (seconds)
Std Dev (seconds)
35 mph Baseline 66 -- Before 168 28 After 100 42 % Change -40% --
Before After
Dis
tanc
e A
long
Cor
rido
r (m
iles)
Travel Time (seconds)
Planning for Traffic Signals Most of the common planning software packages do not
account for basic traffic signal operations, much less adaptive control
Difficult to evaluate/predict the performance of an adaptive system to quantify the benefits
If there are fluctuating traffic patterns, adaptive might be a good solution
If a signal system is being upgraded, often the incremental cost for adaptive is insignificant
Contact Information
Andrew P. Nichols, PhD, PE Director of ITS
Rahall Transportation Institute Marshall University
Huntington, WV 304-696-3203
