Traffic signals operational along S.E. 27th Street

New traffic signals are operational along SE 27th Street in downtown Mercer Island on Friday night. - Chad Coleman/Reporter Staff
New traffic signals are operational along SE 27th Street in downtown Mercer Island on Friday night.
— image credit: Chad Coleman/Reporter Staff

UPDATE: As of Friday, Jan. 27 the lights are working on S.E. 27th Street in downtown Mercer Island.


Two new sets of traffic signals along S.E. 27th Street look ready to go, but have been wrapped in black plastic for weeks.

What gives?

The two new traffic signals in the Town Center were nearly complete in early November when King County’s traffic signal operations and maintenance staff identified a problem with the electronic controllers for the signals during their routine pre-installation inspection of the controllers. According to city engineer Patrick Yamashita, Mercer Island contracts with King County to operate and maintain Mercer Island’s six traffic signals.

“It is cheaper than having the city maintain its handful of lights,” he said.

The faulty signal controllers were sent back to the factory for correction after the problem was identified and then shipped back to King County just before Christmas, Yamashita explained. Since then, King County has inspected, tested and programmed the controllers and found them to be in proper working order. This work took a little longer than usual due to staff schedules around the holidays, he said.

The contractor was scheduled to install the controllers on site and connect them to the signals this week, but the city decided to postpone this work to next week due to the snow and ice, he continued.

The city expects to have the signals operational this week.

To find out more, the city has constructed a traffic signal webpage on the city’s website at as a resource for the public to receive answers to common questions and find helpful information.

The ‘cameras’ placed on top of the signals are called video detection cameras and are used to operate the signals. (Go to the link, “What kind of sensors are used for traffic signals?” on the traffic signal page.) They are used to sense when a vehicle or bicycle approaches the intersection, then the software transmits that information to the signal controller.

The cameras are not for any other function.

“These cameras do not store any images and are focused just on the street,” Yamashita explained. “In other words, they cannot be used as surveillance or as a red light camera.”

As is common for traffic signal projects, city engineers will monitor the operation of the signal after it’s turned on and fine-tune the signal operation based on traffic flow, pedestrian use and other factors.

“We’ve taken time to carefully design the signals system,” Yamashita said. “I hope that it shows in the end.”


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