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Press Releases

For Immediate Release  • October 25, 2012
Staff Contact: Bob Ball, Traffic Engineering Administrator, 303-651-8304

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traffic light

New Flashing Arrows at Longmont Traffic Lights


OCTOBER 25, 2012 - The flashing yellow arrow is a technology that will soon be arriving at Longmont traffic signals.  You’ve probably seen them during the past few years if you have driven in Fort Collins, Aurora, Boulder, Littleton, Colorado Springs, Cheyenne, WY, and many other cities in Colorado and around the country. 

The first flashing yellow arrow in Longmont will be along Airport Road at the Clover Basin Drive traffic signal.  They will gradually be installed at other signalized intersections around Longmont as new left turn arrows are added at intersections or other signal improvements are installed.

The flashing yellow arrow is a new way to advise drivers to yield to opposing traffic, bicycles and pedestrians before making a left turn, and they have safety and operational advantages over the traditional green ball / green arrow signal head.

National studies have shown that they reduce the occurrence of crashes compared with a traditional yield on green ball left turn signals.  Even though it’s well understood that left turns should yield to conflicting traffic and pedestrians, a flashing yellow arrow more effectively sends that “yield” message than a green ball. 

They also allow additional signal timing options, such as the use of a lagging left turn where the left turn phase occurs after the straight through phase for that street.  During much of the day when traffic is not too busy, drivers can usually make their left turns without the green arrow, allowing more green time for through traffic.  When left turns are more difficult, a lagging left turn phase can be called up when needed.  This makes the signalized intersection more efficient overall.

Here’s how the four signal indications in a flashing yellow arrow signal works for drivers who approach an intersection and want to make a left turn:


If you have any questions or would like to learn more, please visit our City of Longmont website or call Bob Ball or Tyler Stamey at 303-651-8304.