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News Release


FOR IMMEDIATE RELEASE: Wednesday, October 13, 2010

Flashing yellow turn arrows to improve safety and traffic flow

In the coming weeks, travelers on Factoria Boulevard will be the first in the city to see new flashing yellow arrows on traffic signals when making left turns. The new signals will be installed at five intersections between Southeast Newport Way and Southeast 32nd Street.

Illustration of flashing yellow light.While the new flashing yellow arrows will look a bit different to motorists, studies suggest they are more intuitive and safer than traditional signals when drivers turn left and must yield to oncoming traffic.

The addition of flashing yellow arrows is part of a larger effort under way to make the city's overall network of traffic signals safer and more efficient with improved technology.

"The flashing yellow arrow gives us a new tool for reducing delays while maintaining safety," said Mark Poch, Bellevue's traffic signals manager. 

Instead of displaying a solid green ball for drivers turning left, the new signals will have a flashing yellow arrow centered above the left turn lane, separate from adjacent signals for through traffic. Studies by the Federal Highway Administration show this display increases safety because it's more effective at getting drivers to yield to oncoming traffic.

Here's the typical sequence for the new left turn signals (video):

  1. Solid red arrow: Drivers turning left must stop and wait.
  2. Solid green arrow: Drivers can proceed with left turn.
  3. Solid yellow arrow: Drivers prepare to stop.
  4. Solid red arrow: A very short clearance interval where drivers turning left must stop.
  5. Flashing yellow arrow: Drivers may proceed with left turn after yielding to oncoming traffic and pedestrians.
  6. Solid yellow arrow: Drivers prepare to stop.
  7. Solid red arrow: Drivers turning left must stop and wait.

Improving traffic flow
In addition to safety, another advantage of the new flashing yellow arrows is flexibility. Left turns on a flashing yellow arrow will soon be allowed during certain times of the day at intersections where left turns are currently allowed on a green arrow only. An example is the left turn from southbound Factoria Boulevard to eastbound Newport Way. Left turns will be allowed on the flashing yellow arrow from 7 p.m. to 7 a.m., and from 9 a.m. to 11 a.m.

Flashing yellow arrows are part of a wider upgrade on Factoria Boulevard utilizing "traffic adaptive" technology. The new traffic adaptive signals will continually monitor vehicle flow in every lane approaching each intersection and automatically adjust signal timing to match traffic flows.

Traffic adaptive technology, in turn, is one element of an Intelligent Transportation System, or ITS, a package of improvements that applies advanced communication and information technology to the transportation system.

"We think ITS in general, and traffic adaptive signals in particular, is a good investment for Bellevue because technology improvements are relatively inexpensive compared to road construction," Poch said. "Simply put, ITS will help the city get more capacity out of its existing transportation system."

Once the new flashing yellow arrows and traffic adaptive upgrades are made in Factoria, plans call for rolling out similar improvements at 22 downtown intersections on Northeast Eighth Street, Northeast Fourth Street and Bellevue Way.

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Contact Information

Traffic Engineering
450 110th Ave. NE
P.O. Box 90012
Bellevue, WA 98009
Contact: Mark Poch
Phone: 425-452-6137
E-mail: mpoch@bellevuewa.gov


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