As a result of a successful experience at the two original locations, the City of Boulder's Transportation Division will install the city's third Flashing Yellow Arrow (FYA) left-turn display at the intersection of Baseline Road and 30th Street on Sunday, Aug. 17. 

The other two FYA signals are located at the following intersections:

• Table Mesa and Tantra drives (installed May 19, 2004); and
• 30th and Walnut streets (installed June 27, 2004)

Here is what the new signals will look like:
	Steady red arrow = Stop. No left turns allowed.
	Steady yellow arrow = Prepare to stop.
	Flashing yellow arrow = Left turns allowed, but must yield to oncoming traffic.
	Steady green arrow = Left turns allowed.

Left-turn Arrows
The flashing yellow arrow traffic signals consist of four arrow lights that are used exclusively for left-turning traffic. The arrow traffic signals are separate from the traffic signals containing circular lights for through traffic.

Benefits of New Left-turn Arrows

• Enables the left-turn control to be varied during the day.
• Eliminates motorist confusion as to the meaning of the circular green light (this is occasionally mistaken as a protected left turn), and the simultaneous circular red light and green arrow (some motorists stop).
• Can be used in all intersection and signal configurations.
• Requires no supplemental signing.
• Eliminates the "left-turn yellow trap" (see demo below) and eliminates the need for a red arrow to avoid the left-turn trap.
• Provides more opportunities for drivers to turn left.
• Does not require optical shielding or precise placement – heads are placed wherever protected left turn heads are normally placed.
• Can also be used for right turns.

The FYA signals are a part of a nationwide study by the Federal Highway Administration that is looking at amending the federal standards for left-turn signals. Based on the successful operation of the FYA over the past several years in locations across the United States, the Federal Highway Administration is planning to add the FYA display in the next update to the federal standards governing traffic signals.

For more information, contact Joe Paulson at (303) 441-3266.

How Left-turn Arrows Fix the Yellow Trap
The yellow trap condition essentially leads the left-turning driver into the intersection when it is possibly unsafe to do so even though the signal displays are correct. During the signal change from "permissive" movements in both directions to a "protected" movement in one direction, a yellow trap is presented to the left-turning driver whose permissive left-turn is terminating. The animated file below illustrates how the yellow trap occurs.

The flashing yellow arrow eliminates the yellow trap. As demonstrated in the illustration below, logically tying the flashing yellow arrow indication to the opposing through green indication completely eliminates the yellow trap.

To view the animation of this, click here!

To view the animation of the proposed solution, click here!

Last Updated on Tuesday, 05 August 2008 06:54