Flashing yellow arrow

How to read it

The MUTCD says traffic facing a flashing yellow arrow may cautiously enter the intersection only to make the turn the arrow shows, yielding to pedestrians in the crosswalk, to vehicles in the intersection and, on a left turn, to oncoming traffic close enough to be an immediate hazard. Oncoming traffic usually has a green light at the same time: Oregon’s manual says it has a steady green, and Florida’s and Michigan’s say the same. The arrow is in a separate turn signal, usually of four sections: from the top a steady red arrow, a steady yellow arrow, the flashing yellow arrow and a green arrow. When the turn’s time ends, the flashing arrow changes to a steady yellow arrow and then to a red arrow; when a protected turn follows, it can go straight to the green arrow. California’s handbook sums it up: the turn is allowed but not protected from other traffic. This page describes the national standard and isn’t legal advice; the rules at a signal are set by state law and vary from state to state.

Also searched as: blinking yellow arrow, flashing yellow left turn arrow.

Why it replaced the green light for left turns

Before it, a permissive left turn was shown with the circular green. In 2006 the FHWA wrote that for many years some engineers had worried drivers turning on it might take it to mean they had the right of way over oncoming traffic, and that no comprehensive research had compared the alternatives. NCHRP Project 3-54 did that over seven years, published in 2003 as NCHRP Report 493. It surveyed the displays in use, among them flashing red arrows in Delaware and California and a flashing circular yellow that Seattle had used since about 1966, and tested drivers’ understanding in comprehension studies and a driving simulator as well as at real intersections. It counted fail-critical responses: a wrong reading that would put the driver in the path of oncoming traffic, with the potential for a crash. The flashing yellow arrow was understood well and drew fewer fail-critical responses than the circular green, and the FHWA called it the best overall alternative.

From trial to standard

The first trial was at three intersections in Montgomery County, Maryland, in September 2000, followed by Tucson, three Oregon jurisdictions and Broward County, Florida. Tucson removed its display over safety concerns raised by city management; the others were still in use when the report was published. The FHWA gave interim approval in March 2006, reporting that drivers intuitively knew what the arrow meant with little or no public information, and the 2009 MUTCD made it part of the national standard. The Manual also allows a flashing red arrow in its place where an engineering study finds every vehicle must stop before turning, such as at wide medians with offset turn lanes.

The yellow trap

A separate arrow also avoids what engineers call the yellow trap. The MUTCD makes all the circular lights on an approach show the same colour, so when one direction’s green ends while the opposite direction keeps its green for a lagging turn, a driver waiting to turn left sees yellow and may try to finish the turn, not realising that oncoming traffic still has a green light (NCHRP Report 493). The FHWA says a flashing yellow arrow in its own signal is easily programmed to avoid it. Michigan’s manual tells drivers that FHWA research found the arrangement moves traffic more efficiently and reduces the chance of crashes.

Look-alikes

A flashing yellow light, round rather than an arrow, allows any movement through the intersection with caution. A steady yellow arrow warns that the turn’s time is ending.