Transit Signal Priority Systems help buses arrive on time, shorten trips up to 20%

Priority access to green signals at intersections can speed travel by public transportation and improve the on-time performance of buses and light-rail vehicles. Transit signal priority systems follow a number of different operating strategies that provide green signals to approaching transit vehicles. Experiences in 10 cities in the U.S. and abroad show up to 20% reductions in bus travel times with transit signal priority. Several studies show significant reduction in travel time variability, with a corresponding improvement in on-time performance.

In the spring of 2000, the King County DOT (Seattle, Washington) implemented a 2.1 mile signal priority system on Rainier Avenue. The system used in-vehicle radio frequency transponders, roadside antennas, and transit priority request generators. The system was designed to control signal timings according to the following logic:

• Approaching transit vehicles were granted extended green intervals and shortened red displays; however, signal coordination between intersections had to be maintained, and the green phases for vehicles on side streets could not be skipped.

The study showed that intersection delay was reduced by an average of 13% (2.3 seconds per vehicle) during the A.M. peak period.

See the related ITS Benefits Database entry for more information on the Seattle study.

Also see the collection of related documents in the Benefits Database for additional documented impacts of transit signal priority.

Past "Benefit of the Month" summaries are also available.

Last Modified: 10/03/2003