Those flashing yellow turn lights are new. How do they work?
Q: I’ve noticed that when new traffic lights are installed, some include a flashing yellow for left turns. What’s different about these lights? Thanks. — Don, Fircrest
A: Much like departed Seattle Seahawks legend Marshawn Lynch, those flashing yellow turn lights are just about that action, boss.
The newfangled signals serve a dual purpose, says Bryan Roberts, the city of Puyallup’s traffic engineer: They remind drivers to take caution while turning across traffic, and they make it so intersections can handle more cars without slowing traffic.
“Our main motivation is a safety improvement to clarify to drivers that you have to yield to oncoming traffic,” Roberts says.
Apart from serving as reminder to drivers that left turns are available, there can be significant benefits in easing congestion at intersections, Roberts says.
The hypothetical example he gave goes as follows:
Imagine a four-way intersection with heavy northbound traffic during afternoon rush hour where many of the drivers want to go left but others want to go straight. A conventional intersection regulated by a green light and a green left-turn arrow would allow northbound drivers to continue traveling, but southbound drivers would have to stop.
Giving northbound drivers who want to turn left a flashing yellow light would allow lighter southbound traffic also to get through the intersection without impeding the turners for too long.
“You can add more capacity,” Roberts says. “You can get more people moving with the flashing yellow.”
Puyallup is adding a handful of the flashing yellow lights at turn signals as the Public Works Department does infrastructure improvements this summer. With any luck, flashing yellow turn lights will have drivers moving through the city like Lynch through the New Orleans Saints’ defense.
“I’m a fan. I think they work,” Roberts says. “I think you’re going to see a lot of these all around the region.”
This story was originally published July 29, 2018 at 6:00 AM.