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Empirical Evaluation of Transit Signal Priority
Transportation Seminar March 6, 2015
Wei Feng, Chicago Transit AuthorityMiguel Figliozzi, Portland State UniversityRobert Bertini, Cal Poly State Univ., San Luis Obispo
(Doug Beghtel/The Oregonian)
Background—Transit Signal Priority
2
PassiveActiveReal-time optimal
Green extensionEarly Green
Kamila Widulinski and Matthew Lapointe (2013)
2
Background—Transit Signal Priority
Evaluation methods
• Analytic: Lin (2002); Abdy & Hellinga (2011)
• Simulation: Furth & Muller (2000); Dion et al. (2004)
• Empirical: Kimpel et al. (2005); Albright & Figliozzi (2012)
Performance measures
• Bus travel time• Schedule adherence• Headway variability• Delay for other vehicles• Lack of effectiveness and efficiency measures/evaluation
Pre-install
Before / after
3
Motivation
Unique set of complementary data sources
TriMet Bus AVL/APC data
City of PortlandSCATS signal phase log data
Intersection vehicle count data
SCATS: Sydney Coordinated Adaptive Traffic System
AVL: Automatic Vehicle LocationAPC: Automatic Passenger Count
4
Research Questions
Current TSP system in Portland:– Effectiveness and efficiency? – Time savings for buses vs. delay to cross street vehicles– Green extension vs. early green phases?– Near-side vs. far-side bus stops?– Any problems and improvement opportunities?
5
Study Corridor
21st 26th 33rd 39th 42nd 50th 52nd 65th 69th 71st, 72nd 82ndMilwaukie
12 SCATS signals
SE Powell Blvd.
Bus Route 9
Bus Route 66
Near-side: 26th EB26th WB
33rd EB 42nd EB43rd WB
72nd EB
Far-side: 50th EB50th WB33rd WB
39th EB39th WB 72nd WB
52nd EB52nd WB
65th EB65th WB
69th EB 71st EB
Far-side (12)
Near-side (6)Stop-to-stop segment
6
Bus stop-to-stop segments
6 near-side segments
12 far-side segments
7
SCATS Signals
0
20
40
60
80
100
120
140
E W E W E W E W E W E W E W E W E W E W E W E W
MKE 21st 26th 33rd 39th 42nd 50th 52nd 65th 69th 71st 72nd
Seco
nds
Intersections / Directions
Median Cycle Length, Green phase and red phase duration
Red
Green
8
Data Integration
Bus ALV/APC Database
SCATS Vehicle Count Database
SCATS Signal Phase Log Database
Bus Stop-to-Stop Trip Database
TSP Performance
Evaluation
9
Bus Stop-to-Stop Trip Attributes
• Bus departure/arrival time
• Passenger activities
• Signal phase start/end time
• Priority request
• Upstream/downstream distance
Input data
• Probability of arriving at
intersection in:
– Green
– Red
– Green extension
– Early green
• Signal delay
• Time savings
Output variables
10
Bus Time Saving (Early Green)
𝑑𝑑1
Arrival time
Departure time
𝑅𝑅𝑗𝑗𝑠𝑠
𝑅𝑅𝑗𝑗𝑒𝑒 = 𝐸𝐸𝐸𝐸𝑗𝑗𝑠𝑠
𝑎𝑎𝑎𝑎𝑖𝑖
𝑑𝑑𝑎𝑎𝑖𝑖
𝑅𝑅𝑗𝑗+1𝑠𝑠 𝑅𝑅𝑗𝑗+1𝑒𝑒
𝑣𝑣𝑚𝑚𝑚𝑚𝑚𝑚
𝑑𝑑2 𝑣𝑣𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑙𝑙𝑎𝑎𝑟𝑟
𝐸𝐸𝐸𝐸𝑗𝑗𝑒𝑒
EB 39th
speed (mph)
Den
sity
0 5 15 25 35
0.00
0.10
0.20
am
11
Bus Time Saving (Green Extension)
𝑑𝑑1
Arrival time
Departure time
𝑅𝑅𝑗𝑗𝑠𝑠 𝑅𝑅𝑗𝑗𝑒𝑒
𝑎𝑎𝑎𝑎𝑖𝑖
𝑑𝑑𝑎𝑎𝑖𝑖
𝐸𝐸𝐸𝐸𝑗𝑗𝑒𝑒 = 𝑅𝑅𝑗𝑗+1𝑠𝑠 = 𝑎𝑎𝑟𝑟
𝑅𝑅𝑗𝑗+1𝑒𝑒
𝑣𝑣𝑚𝑚𝑚𝑚𝑚𝑚
𝑑𝑑2 𝑎𝑎𝑙𝑙
𝐸𝐸𝐸𝐸𝑗𝑗𝑠𝑠
12
Key Performance Measures
– TSP Frequency
– TSP Effectiveness (for each TSP request)Probability of benefiting from a TSP phaseExpected time saving
– TSP Efficiency (for each TSP phase)Probability of being beneficial to a TSP requestExpected time saving per second of TSP phase duration
13
TSP Frequency
0102030405060708090
26th 33rd 39th 42nd 50th 52nd 65th 69th 71st 72nd
Average number of bus trips per day
requested TSP did not request TSP
0102030405060708090
26th 33rd 39th 42nd 50th 52nd 65th 69th 71st 72nd
Average number of TSP phases per day
Green Extension (GE) Early Green (EG)
14
When A TSP Request Will Benefit from GE/EG
Benefit from Green Extension
Benefit from Early Green
Green
GE
Red-GE
Cycle
Green
Red-EG
EG
Cycle
15
Potential Results of A TSP Request
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
on-time EG = Red/Cycle on-time EG = Red/Cycleon-time GE = GE/Cycle on-time GE = GE/Cycle
near
near
near
16
Actual Outcomes of TSP Requests
TSP request
No TSP phase within the cycle
TSP phase within the cycle
GE
EG
Both GE and EG
Neither GE or EG
GE: Green ExtensionEG: Early Green
17
Actual Outcomes of TSP Requests
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
Neither GE nor EG EG Both GE and EG GE
near
near
near
18
TSP Effectiveness
Bus trips that request TSP
Green extension
TSP request
No TSP phase within the cycle
TSP phase within the cycle
a b c
1 3
Early
On-time
Late3
1
a
b
c
Time saving
Effectiveness Benefit
GE or/and EG
2
19
TSP Request Outcomes for GE
a b cd
near
near
near
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
d: no GE a: late GE b: on time GE c: early GE
20
TSP Request Outcomes for EG
a b cd
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
d: no EG a: late EG b: on time EG c: early EG
near
near
near
21
Actual TSP Effectiveness
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
on-time EG on-time EG on-time GE on-time GE
near
near
near
22
Ideal TSP Effectiveness
0%10%20%30%40%50%60%70%80%90%
100%
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
on-time EG = Red/Cycle on-time EG = Red/Cycleon-time GE = GE/Cycle on-time GE = GE/Cycle
near
near
near
23
Passenger Time Saving per TSP Request
∑𝑖𝑖 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑠𝑠𝑎𝑎𝑣𝑣𝑇𝑇𝑠𝑠𝑠𝑠 𝑓𝑓𝑓𝑓𝑓𝑓𝑇𝑇 𝐸𝐸𝐸𝐸𝑖𝑖∑𝑖𝑖 𝑇𝑇𝑇𝑇𝑇𝑇 𝑓𝑓𝑇𝑇𝑟𝑟𝑟𝑟𝑇𝑇𝑠𝑠𝑎𝑎𝑖𝑖
∑𝑖𝑖 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑠𝑠𝑎𝑎𝑣𝑣𝑇𝑇𝑠𝑠𝑠𝑠 𝑓𝑓𝑓𝑓𝑓𝑓𝑇𝑇 𝐸𝐸𝐸𝐸𝑖𝑖∑𝑖𝑖 𝑇𝑇𝑇𝑇𝑇𝑇 𝑓𝑓𝑇𝑇𝑟𝑟𝑟𝑟𝑇𝑇𝑠𝑠𝑎𝑎𝑖𝑖
0
5
10
15
20
25
39th 42nd 50th 52nd 65th 69th 71st 72nd
seco
nds
from GE from EG
24
TSP Phase Triggered by TSP Requests
TSP phase
No TSP request within the cycle
TSP request within the cycle
EB
WB
Both EB and WB
Neither EB or WB
GE or EG
25
% of GEs Associated to TSP Requests From
0%10%20%30%40%50%60%70%80%90%
100%
39th 42nd 50th 52nd 65th 69th 71st 72nd
Neither EB nor WB EB EB and WB WB
26
% of EGs Associated to TSP Requests From
0%10%20%30%40%50%60%70%80%90%
100%
39th 42nd 50th 52nd 65th 69th 71st 72nd
Neither EB nor WB EB EB and WB WB
27
TSP Efficiency
TSP phase
No TSP request within the cycle
TSP request within the cycle
a b c
1 2 3
Early
On-time
Late3
2
a
b
c
Time saving
Efficiency Benefit
GE or EG
Bus trips that request TSP
Green extension
28
Actual Green Extension Efficiency
a b cd
0%10%20%30%40%50%60%70%80%90%
100%
39th 42nd 50th 52nd 65th 69th 71st 72nd
out of cycle c: early b: on-time a: late
29
Actual Early Green Efficiency
a b cd
0%10%20%30%40%50%60%70%80%90%
100%
39th 42nd 50th 52nd 65th 69th 71st 72nd
out of cycle c: early b: on-time a: late
30
TSP Efficiency (Time Saving vs. Delay)
TSP phase
Major street bus and other vehicles time saving
Minor street other vehicles delay
Major street other vehicles time saving
GE or EG
31
Bus Passenger Time Saving per EG
020406080
100120140
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
seco
nds
near-side far-side
∑𝑗𝑗 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑠𝑠𝑎𝑎𝑣𝑣𝑇𝑇𝑠𝑠𝑠𝑠 𝑓𝑓𝑓𝑓 𝐸𝐸𝐸𝐸𝑗𝑗∑𝑗𝑗 𝐸𝐸𝐸𝐸𝑗𝑗
32
Bus Passenger Time Saving per GE
020406080
100120140
EB WB EB WB EB WB EB WB EB WB EB WB EB WB EB WB
39th 42nd 50th 52nd 65th 69th 71st 72nd
seco
nds
near-side far-side
∑𝑗𝑗 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑠𝑠𝑎𝑎𝑣𝑣𝑇𝑇𝑠𝑠𝑠𝑠 𝑓𝑓𝑓𝑓 𝐸𝐸𝐸𝐸𝑗𝑗∑𝑗𝑗 𝐸𝐸𝐸𝐸𝑗𝑗
33
Vehicle Time Savings and Delay
34
Green Extension Efficiency
Assume single occupancy vehicles
0
10
20
30
40
50
60
39th 42nd 50th 52nd 65th 69th 71st 72nd
seco
nds
Minor street vehicle delay Major street vehicle time savingMajor street passenger time saving
35
Early Green Efficiency
Assume single occupancy vehicles
0
10
20
30
40
50
60
39th 42nd 50th 52nd 65th 69th 71st 72nd
seco
nds
Minor street vehicle delay Major street vehicle time savingMajor street passenger time saving
36
Summary of Findings
Green extension • Too many late green extension phases• Time savings ≈ Delay
Early green • Time savings > Delay
TSP performance • Vary significantly across intersections• Big gap between actual and ideal performance
37
Conclusions
• Proposed TSP performance measures can help identify problems/improvement opportunities and support planning decisions
• Findings from this study may be site-specific, but the methodologies are transferable to other corridors/cities
• TSP effectiveness and efficiency can be greatly affected by control logic, parameter calibration and signal detection/communication reliability
38
Future Work
• Consider vehicle queuing effect when estimating bus arrival time probabilities at intersections
• Utilize new and higher resolution data such as:– 5-second bus AVL data (finer bus trajectory between bus stops)– TSP Optical detector log data (priority log in/out records)
39
Acknowledgements
Steve CallasDavid Crout
Peter KoonceWillie Rotich
40
Questions?
41
On Average
TSP request
On-time
No TSP phase within a cycle
Within a cycle but early
Within a cycle but late
GE EG
1.5% 10%
2.5% 5%
25% 1%
55%
Bus time saving 0.3s 0.5s
Passenger time saving 7.5s 10s
= 100%
Actual Ideal
GE EG
6% 27%
0% 0%
0% 0%
67%
= 100%
42
On Average
TSP phase
On-time
No TSP request within a cycle
Early
Late
GE EG
5% 40%
3% 30%
64% 8%
Bus passenger time savings 20s 90s
28% 22%
Duration 7s 11s
Major street vehicle time savings
Minor street vehicle delay
60s 300s
80s 200s
=100% =100%
Actual Ideal
100%
0%
0%
0%
GE or EG
=100%
43
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