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Metro Transit Division

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Seattle, WA 98104
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Transit Signal Priority tests a success,
more signal synchronization planned countywide

New Transit Signal Priority technology allows specially equipped buses to communicate with an approaching traffic signal and ask it to hold the green light for the bus. A transponder installed on the bus sends a signal to a controller on the traffic light.

A new high-tech system aimed at moving Metro buses and passengers faster and more smoothly through busy arterials has been shown to cut travel time by 8 percent along the busiest route in the Metro system. The results were announced today as King County moves ahead with a program to offer grants to cities to synchronize traffic signals at 80 intersections along transit routes throughout the county.

The Transit Signal Priority (TSP) technology allows specially equipped buses to communicate with an approaching traffic signal and ask it to hold the green light for the bus. A transponder installed on the bus sends a signal to a controller on the traffic light.

The test results were obtained along a 2.1-mile stretch of Route 7 on Rainier Avenue South, a route that has the highest ridership of any in the Metro system with more than 2-million passenger trips per year into downtown Seattle. The results, although not necessarily representative of all intersections under all conditions, represent a snapshot of system performance and are very encouraging. Among the key findings in a recent analysis of the test, conducted in association with SEATRAN:

  • Passengers waited 34 percent less time at intersections.
  • Buses made an average 24 percent fewer stops at signalized intersections, with some intersections experiencing up to a 43 percent reduction in stops.
  • Passengers riding the length of the Rainier Avenue corridor made the trip an estimated 8 percent faster.
  • Holding the green light for buses produced only a minimal delay on cross streets that was likely unnoticeable to the driver.

Voter approval of the recent "Yes on Metro" Proposition One measure is now funding a new $1.5-million initiative to help local cities throughout the county to synchronize traffic signals, in particular along arterials used by transit. In the first year of this new program, $400,000 will be available for synchronization of 80 intersections to improve the speed and reliability of transit service operating in increasingly congested corridors countywide. New partnership agreements with participating cities will be announced later this spring.

King County and the cities of Seattle and Shoreline are collaborating on another TSP project on Aurora Avenue North between Winona Avenue and N. 205th Street, which includes 21 intersections equipped with TSP.

The results of the Rainier Avenue and Aurora Avenue projects will be used to improve strategies on other active, funded TSP projects on which King County is collaborating with local cities. These projects include the following corridors:

  • Lake City Way in Seattle
  • 15th Avenue W. and 1st Avenue South in Seattle
  • State Route 99 / Pacific Highway South in Federal Way, Kent, Des Moines, SeaTac, and Tukwila
  • NE 124th Street in Kirkland
  • 148th and 156th Avenue NE in Redmond
  • Downtown Renton

"This is great news. As our roads and arterials become more congested, it shows that Ďintelligent transportation systemsí can cut travel times and in particular make the experience of riding a bus a smoother and more pleasant one," said King County Executive Ron Sims.

Transit riders who experience a smoother and more comfortable ride with fewer stops are more likely to continue riding. Improved service means people who have not taken the bus before may be more likely to try it. Fewer stops also mean reductions in the driverís workload, fuel consumption, vehicle emissions, and maintenance costs.

Rainier Avenue is on the Regional Arterial Network (RAN), a network of principal arterials that is the focus of King County DOTís regional mobility improvements. Governor Gary Locke recently included funding for corridor congestion relief in his transportation request bill, SB 5327. The Rainier Avenue TSP program is a joint effort between the transportation departments of the City of Seattle and King County to implement the Seattle Transit Initiative to improve flow on heavily traveled transit corridors.

"As we showed with our traffic signal optimization along Aurora Avenue North and Delridge Way SW, the goal is to maximize the greens and reduce reds," said Seattle Mayor Paul Schell, whose city owns and operates the traffic signal controllers used in the Rainier and Aurora TSP projects.

Updated: Feb. 15, 2001