its and planning for transit priority in broward county, florida

Center for Urban Transportation ResearchUniversity of South Florida

ITS and Planning forTransit Priority in

Broward County, FloridaTRB Workshop on Signal Control

Priority for Transit VehiclesJanuary 11, 2004

Lawrence T. Hagen, P.E., PTOE


Agenda

BackgroundHistory of project Objective of project

Preemption vs. PriorityLessons LearnedFuture DirectionsConclusions


Background

Project was funded with public safety funds.Goal was to provide preemption for

emergency vehicles.Transit priority was added as an ancillary

benefit.Objective was to accommodate both high

priority calls (preemption) and low priority calls (priority).


GPS System Basic Operation Vehicle GPS receiver obtains vehicle position, speed

and heading information from GPS satellites Vehicle equipment transmits this information to

intersection via radio Intersection radio receives this information. If vehicle is approaching intersection in a predefined

approach corridor and requesting priority, the phase selector provides an output to the traffic controller's preemption input

The traffic controllers preemption input is programmed to hold the green light or cycle to the green light for the approaching vehicle


Signal Preemption vs. Signal Priority

Preemption – a need for a special mode of operation that causes you to leave normal operation suddenly.

Priority – a need to enhance or prefer a particular movement while maintaining normal operation.


45%

35%

20%

Main StreetCross StreetLeft Turns

Normal Cycle - Preemption Call


45%

35%

20%


Normal Cycle - Priority Call


55%30%

15%


Green Extension Cycle


45%

35%

20%




55%

30%

15%Main StreetCross StreetLeft Turns

Early Green Cycle


Lessons Learned

BE CAREFULL OF PEDESTRIAN TREATMENT

NOT ALL CONTROLLERS CAN HANDLE TRANSIT PRIORITY AND PREEMPTION

SYSTEM WORKED TOO GOODNOT ALL CONTROLLERS CAN HANDLE

DESTINATION-SPECIFIC PREEMPTIONCONTROL SYSTEM LIMITATIONS


Turn Signal MonitoringVehicle unit senses state of the turn signals Information is transmitted to intersectionThe intersection the vehicle is approaching, can

then relay the priority request to the next intersection in the direction that the vehicle will be turning

The outputs of the phase selector may also be varied depending on the state of the turn signalThis allows different greens to be displayed depending on

the intended direction of the vehicle


Turn Signal Dependant Mode

Limiting factor will most likely be the number of preemption inputs on the controller.

Typical use would be to only display protected left turn arrow if vehicle is turning left


Turn Signal Dependant Mode Example


Broward County Traffic Control System


45%

35%

20%




55%

30%


Early Green Cycle


Future Directions

Destination-specific transit priorityExample: Left-turning bus


45%

35%

20%




55%

30%


Early Green Cycle


45%

35%

20%




45%

30%

25%


Early Left Cycle


Future Directions

Destination-specific transit priorityExample: Left-turning bus

Communication to downstream signalsEspecially short block lengths without transit

stops

Improved tracking systems – continuous detection


Conclusions

Implementing transit priority is doable, it is just not always as easy as it sounds – many issues need to be addressed.

Many existing legacy traffic systems (pre-NTCIP) may have limitations.

Standards are still in the developmental stage.

Opportunities are endless!


Questions?

Larry [email protected]

its and planning for transit priority in broward county, florida

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