CHOKEPOINTS

Responsive traffic signals around Seattle catch drivers snoozing

Jun 30, 2016, 8:00 AM

Lynnwood, traffic, signal...

Some traffic signals in the Puget Sound area are smart enough to detect gaps in traffic. That can backfire if people aren't paying attention to the traffic lights. (City of Lynnwood)

(City of Lynnwood)

We’ve all been there: sitting at a traffic light, waiting patiently to go, only to have the person in front of you buried in their phone, not aware the light has changed. What you might not realize is the signal picks up that gap and takes away the time drivers have to get through the intersection.

As it turns out, some signals are smart enough to notice gaps in traffic.

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“One of the things I’m noticing, and this is definitely part of the left-turning queues … I’ll get a call that only five cars got through, and when I’m watching I’m seeing that someone in the queue is not going with the others,” Lynnwood traffic engineer Paul Coffelt said.

The signals are designed to detect a queue of vehicles.

“When the end of the queue is sensed by the detection equipment, it goes yellow-red, and yeah, maybe only five cars got through because it gapped-out,” Coffelt explained.

Drivers wanted more responsive signals, Coffelt said. There’s a flip side to that, though. They know where you’re not paying attention.

“In the past, that was wasted green time,” he said. “We’d be serving a queue that wasn’t there anymore. We sense the end of the queue, and we say ‘on to other demands.'”

And there is always demand in the other directions. That means drivers need to pay more attention to driving, and less attention to their phones.

“We have to get people to turn off the phone, put it in the trunk, whatever they have to do to pay attention and keep moving so it’s a good experience for all of us,” Coffelt said.

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Responsive traffic signals around Seattle catch drivers snoozing