Retimed traffic lights mean less waiting, city claims

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February 9, 2004 // UPDATED 2:51 pm - April 24, 2007
By: Scott Russell
Scott Russell

For the first time in a decade, the city retimed the Downtown traffic lights and -- if the computer models are correct -- you should be hitting 10 percent fewer red lights and have at least 20 percent less wait time, according to city estimates.

Roger Plum, senior transportation engineer for city consultant SEH, said the entire signal network changed in mid-January.

"Nothing has remained the same," he said. "We have tried to improve the relationships between the starts of greens at each of the intersections as you pass through the Downtown area."

The new timing system factored in several significant changes in the Downtown commuter landscape. First, the lights assume congestion has slowed traffic since the last retiming, Plum said.

"Ten years ago, it seemed like the predominant speed around Downtown was around 30 mph, now it is closer to 25 mph," he said. "We did use that speed as a major assumption in how people are traveling Downtown."

The new system also favors light-rail transit (LRT) and buses, minimizing travel time on a per-person, not a per-vehicle basis. "We had to retime everything else in the Downtown area around [LRT]," Plum said.

Plum continues to tinker with the system. He has received mostly positive comments from people in his office and city Public Works staff, he said.

He did get a complaint from bus drivers. The new system initially caused significant bus backups at Nicollet and Marquette avenues where they crossed the new LRT lines at 5th Street South, the biggest glitch to date, Plum said.

The device that signals the traffic lights of an oncoming LRT vehicle was not working 100 percent of the time, he said. The device was set to assume a train was at the intersection every traffic light cycle -- holding up vehicle traffic regardless of whether a train was there or not.

As a temporary fix, Plum said the city adjusted the traffic lights to take time away from 5th Street and gave it back to Nicollet and Marquette.

John Hotvet, Public Works' project manager, said the city plans a second phase for light retiming later this year.

A few months after LRT's April launch, the city will do traffic counts at all Downtown intersections to better time the system, Hotvet said. Waiting until June or July will give traffic patterns a chance to settle -- both those riding LRT and drivers who might adjust their commutes to avoid the LRT.

Plum said people with comments on the new timing could e-mail him at rplum@sehinc.com.