(Blue Diamond Road) Corridor Study - Regional Transportation ...

6. SR-160 Corridor Improvement Plan RTC SR-160 Corridor Study
6.4.3 Bus Signal Priority
AASHTO’s “Guide for Park & Ride Facilities” 12 lists eleven different types of Bus Signal
Priority strategies, which are as follows.
Unconditional priority: priority is given whenever a bus detector requests it from
signals.
Conditional priority: includes variables that may limit priority given, such as bus
occupancy, queue length, and time since last priority was granted.
Phase: part of the traffic signal time cycle allocated to any combination of traffic
movements receiving right-of-way simultaneously during one or more intervals.
Green extension: green phase is extended when bus is nearby to allow it to go
through.
Special phase: a special green phase is injected into the normal phase sequence
while all other phases are stopped.
Compensation: green time is allocated to a non-priority phase that was truncated to
make up for lost time.
Red truncation: if the bus arrives at an intersection during the beginning or middle
of a red phase, the red phase is truncated and green phase is injected to allow the
bus to go through.
Early start: when bus arrives at intersection during a red, green follows quicker than
usual.
Green recall: a green phase is displayed each cycle whether demand exists or not.
Synchronization: timing groups of traffic signals along an arterial to provide for the
smooth movement of traffic with minimal stops.
Phase suppression: one or more non-priority phases with low demand may be
omitted from the normal phase sequence.
The strategy implemented at queue-jumping lane intersections would likely include one of
the TSP solutions listed above, or it could simply provide a green signal to the queuejumping
lane approximately five to ten seconds prior to the green signal for the general
traffic lanes, either on every cycle or only when a bus is detected. (All buses will be
equipped with TSP emitters.) Such decisions would need to be made on a case-by-case
basis at each intersection.
TSP can be programmed to activate only in the peak direction during peak periods, or only if
buses are running behind schedule (as determined by the bus operator). It is likely that
12 Ibid, p. 50
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