transit signal priority
TRANSCRIPT
Impact on intersection efficiency and safety
for all users
Transit Signal
Priority
Authors
Stephan Kellner, Eng., P.Eng., MS
François Bélisle, Eng. jr., B.Sc., M.Sc.
2
Presentation outline
3
Introduction
Basic operation principles
Operation strategies
System test
Considerations
Impact on all users
Conclusion
Introduction
4
Transit Signalisation Priority
(TSP)
− Operational strategy to
facilitate transit vehicle
movements (1)
− Enhances transit
movements without
undue impact on other
users
Basic operation principles
5
Vehicle detected upstream
Requests
− All or some requests are
accepted
− Request transmitted to
traffic controller
Detected vehicle passes
through intersection
Confirmation transmitted to
controller
Return to normal operation
Basic operation principles
6
On-board interface
Emitter
Check-in detection zone
Check-out detection zone
Traffic controller
(w/ or w/o interface)
Optional: connection to
centralized traffic control
centre (CTC)
Operation strategies
7
Passive systems (w/o detection)
− Optimization to enhance
transit operation
• Cycles
• Timings
• Offsets
May be sufficient for certain
agencies and certain
intersections
Operation strategies
8
Active systems (w/ detection)
− Green extension
− Red truncation
− Phase rotation
− Addition of transit phases
May be too costly for certain
problems and agencies
May have too much impact on
other users
Operation strategies
9
Simple strategies
− All requests from vehicles
executed
• Detection upstream,
according to speed
• Assumes constant speed
• Works w/ green extension
Complex strategies
Transit priority for vehicles
behind schedule only
- Intelligent interface, or
- CTC
Eliminating queues in front
of transit vehicles
- Queue detection needed
- Exact location of transit
vehicle
System test
10
System test
− TSP can be a complex
system
− Apply software integration
procedures
Establish procedures to
− Test
− Verify
− Validate
Testing of all components
On test-bench
Before installation
After installation
Validation of detection zones
with equipment in place
Validation of communication
with CTC
Considerations
11
Physical
− Bus stop location (far-
side, near-side)
− Detection (equipment,
zones)
− Screening of requests
(vehicle ready, stopped,
behind schedule, etc.)
Considerations
12
Traffic signals
− Equipment compatibility
− Communication
equipment
− Link with CTC
Considerations
13
Strategic
− Delays due to signals?
− Regularity impacted by
signals?
− Use of passive TSP?
− Use of active TSP?
− Other agencies?
− Cost/benefit ratio
positive?
Expected results (2,3,4,5)
Signal priority mostly affects
travel time variability
May not reduce wholesale
travel time
Often unrealistic to expect to
reduce number of buses
Impact on all users
14
TSP is best for schedule
reliability
Often side benefit of travel-
time savings
One priority request can
impact another
Vehicles running ahead of
schedule are not positive
Impact on other users
Cars
Pedestrians
Cyclists
Other transit users
The extra time for transit comes
from somewhere…
Impact on all users
15
Safety considerations
− Undue delays create
unsafe behavior (6)
− Inconsistent signal timing
= unexpected signal
timing
− Elevated signal cycles
− More or less congestion
at intersections
Impact on all users
16
Pedestrians and cyclists
− Bus stop location vs
• Walking distances
• Bike path routing
− Queue jumps vs cyclists
− Pedestrian crossing times
Conclusion
17
TSP can have positive
impact on transit operations
(regularity)
TSP has impacts on other
users
TSP can be costly
Analysis of transit needs and
agency procedures is
important
Considering all users in cost-
benefit analysis
References
1. Transit Signal Priority: A Planning and Implementation Handbook. ITS
America. 2005.
2. Transit Signal Priority: Advanced Control Logic to Really Benefit Transit.
Peter G. Furth, Northeastern University. Boston, MA. 2009.
3. TCRP 110: Commonsense Approaches for Improving Transit Bus
Speeds. TRB 2014.
4. Simulation of Transit Signal Priority Using the NTCIP Architecture.
Hongchao Liu, Texas Tech University; Alexander Skabardonis, University
of California, Berkeley; Meng Li, University of California, Berkeley.
Journal of Public Transportation, 2006 BRT Special Edition.
5. Transit Signal Priority Systems Application and Technology Investigation.
Christopher G. Hedden. NJDOT. 2009.
6. Traffic Safety on Bus Priority Systems, World Resources Institute report,
2014.
