Retiming traffic lights should help improve downtown traffic flow

Seattle officials said Wednesday that they've synchronized signals at 258 downtown intersections for the first time in more than two decades and promised quicker, less polluting trips through the central business district will result.

Drivers will still encounter red lights between Jackson Street, Denny Way, Boren Avenue and Elliott Bay, but the city predicted a 12 percent reduction in stops and 40 percent shorter travel times through the 1.25-mile long district.

Changes were needed, said spokesman Rick Sheridan of the city Department of Transportation.

"Roadway conditions have actually changed in the course of two decades," he said.

The change reflects past developments and future complications. Officials said the last full downtown signal synchronization was done 21 years ago. Since then, one additional sports stadium and several other downtown buildings were built, including a shopping mall on Pine Street. Cars and trucks have been largely moved off the downtown portion of Third Avenue, which can now be used its entire distance only by transit buses.

And traffic promises to become more congested if the Alaskan Way Viaduct is shut down for reconstruction, or completely removed, and its traffic shifts to city streets.

Mayor Greg Nickels, announcing the downtown signal changes Wednesday, said they should help reduce motorist frustration and cut fuel consumption and cut greenhouse gas emissions.

Sheridan quoted the mayor as saying, "the best car trip is one not taken. However, we all have to drive and based on that the city is committed to making travel ... faster and more efficient."

The changes will mean a motorist entering the downtown core area should get through it "with a minimum number of stops" even during rush hours, Sheridan said, and during off-peak hours travel times "should be even better."

In a separate set of changes, the city last year resynchronized signals at 193 other intersections around the city; and based on subsequent checks, travel times there improved an average of 40 percent during morning peaks, 28 percent in afternoon peaks and 33 percent at mid-day, the city said.

The new downtown signal changes will slightly favor north-south travel during rush hours, with 55 percent of traffic cycle time open to traffic in those directions and 45 percent regulating east-west travel, Sheridan said. The cycles also can be changed to reflect events at Seattle Center and the sports stadiums.

Signal timing and slow travel through the city's downtown area has long been a source of motorist frustration and questions.

The city has retimed lights on specific corridors year to year but the downtown change is the first "comprehensive effort" done since the late 1980s, Sheridan said.

City staff spent 18 months and about $300,000 making the changes downtown. Work on 150 more intersections will occur this year, including signal changes on Rainier Avenue South, in West Seattle and the area near the Fremont/Bridge Way area north of the Lake Washington Ship Canal.

In addition to the signal re-timings the city plans another $20 million in intelligent-transportation system improvements. Next year it plans to triple the number of traffic cameras, add 15 more streetside message signs and start an online traveler-information map.

New data will include travel times on arterial routes, information for truckers and computer-managed traffic signals on First and Fourth avenues south and Elliott Avenue.