Flashing yellow traffic lights: What do they mean?

BOISE, Idaho (KBOI ) - Different traffic lights are popping up more frequently in some parts of town, and they're causing some confusion for drivers.

They're called flashing yellow lights, and mean that drivers should yield to oncoming traffic and pedestrians before making a left turn. Once the road is clear, they can make the turn.

While they're not a new addition, these lights can be found at 100 of 400 intersections with traffic signals in Ada County. They're similar to other green left turn yield lights, but the Ada County Highway District says research shows these lights are more intuitive for drivers.

"Often times drivers see green and they think 'go,'" Ada County High way District Spokeswoman Christine Myron said. "When they see yellow, they often associate that with caution and having to yield."

These flashing yellow lights have been in some parts of town since 2010, starting on State Street. Since then, the Ada County Highway District has been installing more of them around Ada County.

The lights are meant to speed up commute time by increasing movement in the intersections and decreasing the amount of time drivers spend waiting at traffic lights.

"Nobody likes to sit at a traffic signal, especially when they would have an opportunity to turn," Myron said. "When they can see that no traffic is coming for half of a mile, the worst thing you can have to do is wait."

If you were hesitant the first time you saw them, you weren't alone.

"Anytime you make a change or you implement a new traffic signal or sign there's certainly a learning curve, so it does take people a bit of time to recognize how they should respond," Myron said.

On June 22, a Boise woman died in a crash near Micron after colliding with a truck and a horse trailer at an intersection with a flashing yellow light.

"Certainly safety is a huge priority to us, so we will continue to evaluate those intersections where we've installed the flashing yellow arrows," Myron said.

Myron added that they evaluate each intersection on a case-by-case basis, and that intersections must have certain criteria in order to be determined safe to place one of the flashing yellow lights there.

Ada County Highway District looks at variables like traffic volume, pedestrian volume, sight distance and speed of travel to pick which intersections could see the additions.

"Typically we only install them on roads that have a speed limit of 45 mph or less," Myron said.

The lights also can't be used at intersections with more than one turn lane.

There has been no public information sent out about these lights, but the ACHD says people have been catching on quickly, and are thankful for the quicker commute they create.

"So far so good and we'll continue," Myron said. "I know we have an ongoing list of places where we will continue installing them so people may notice them along their commute more in the future."

Here's another interesting fact: these flashing lights can be turned on and off throughout the day. For example, if there is a peak time for pedestrian crossing at an intersection, the Ada County Highway District can turn the lights off so that drivers will no longer have an option to turn on the flashing yellow.