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Flashing Yellow Left-Turn Arrows                 


What are flashing yellow left-turn arrows?

The Federal Highway Administration is now allowing departments of transportation to use flashing yellow left-turn signals as an option on certain roadway intersections. In St. Louis, MoDOT has installed flashing yellow left-turn arrow signal lights at nearly 100 intersections in the area.  The first three in the state were istalled in West St. Louis County area (on eastbound and westbound Rte. 340 (Olive Blvd.) at Mason, on eastbound and westbound Rte 340 at Barnes West/Heritage Place, and on eastbound and westbound Rte. 340 at Ross/Questover) as a test project. The first signals installed after Federal Highway allowed DOTs to use them were at Interstate 70 and Route K in St. Charles County.  The department is looking at other locations and will add them as appropriate.

MoDOT Traffic Operations Engineer Greg Owens says the new signal lights improve safety and reduce traffic delays. “With the new flashing left-turn arrow, drivers can make a left turn when this light is on, when it is safe to do so,” he says. “This essentially gives drivers two ‘chances’ to make it through the signal, resulting in less wait time at the intersection.”

MoDOT will consider installing these signals, where appropriate, as the department continues to upgrade its traffic signals across the state.

How does a flashing left-turn arrow work?   

A flashing yellow arrow means left turns are permitted, but you must first yield to oncoming traffic and pedestrians and then proceed with caution. The flashing yellow arrow does not replace the solid yellow arrow and it’s meaning; it does replace the green “ball” indication as a signal for a yielding left turn.

Drivers should always remember: a flashing yellow = turn with caution.

How should drivers approach a flashing yellow left-turn signal?    

Drivers should stop at the intersection, and yield to oncoming traffic. If and when it is safe, make your left turn and proceed through the intersection. When the available time for the flashing yellow arrow ends, the solid yellow left-turn arrow begins. The solid yellow retains its standard meaning: the left turn signal is about to go to red and they should prepare to stop, or prepare to complete their left turn if they are in the intersection.

Why not use a solid green light instead of the flashing yellow arrow?

The solid green light is often misunderstood as a left turn indicator. This is because drivers naturally think “green means go”. Traffic making a left turn on a solid green light some times does not yield to oncoming traffic, which can result in more crashes. The flashing yellow arrow allows left turns but at the same time communicates the “caution” message to drivers. The flashing yellow left-turn arrow is especially effective at intersections with high volumes of traffic.

The flashing yellow left-turn arrow will be operational when traffic volumes permit, typically during non-rush hours.

Are other states using this type of signal?

Yes. The Federal Highway Administration has approved the use of flashing yellow arrow in the latest version of the Manual on Uniform Traffic Control Devices.

For more information:

Please contact MoDOT at 314-275-1500 or 1-888-ASK-MODOT

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