CORRECT FLASHING YELLOW ARROWS INSTALLATION

Correctly installed, Flashing Yellow Arrows (FYA) can make an intersection much safer by preventing the hazard known as Yellow Trap. But incorrect installation can cause yellow trap and make the intersection more dangerous.

The following rules must be followed:

1. A Flashing Yellow Arrow face (FYA) shall not be used if any of the following conditions exist:
   • The left turn has a lane shared with other movements (including a single-lane approach).
   • The permissive left turn must cross more than one stream of traffic.
   • The permissive left turn follows an unusual path.
   • Inadequate sight distance.
   • It is desired to protect a pedestrian phase from permissive left turns.
2. A Flashing Yellow Arrow face should not be used if any of the following conditions exist:
   • The left turn crosses three or more oncoming thru lanes.
   • Two or more lanes make the left turn.
   • The speed limit is higher than 45 mph.
   • Left turning drivers can't see through oncoming left turn vehicles to see oncoming straight-ahead vehicles.
3. If FYA exists on a road with left turns in both directions, FYA faces must exist in BOTH directions.
   • Exception: When an FYA face is not allowed in one direction, an Exclusively-Protected left-turn face must be used instead.
4. Each FYA must be flashing at ALL TIMES when the ONCOMING circular green is lighted.
   • The FYA must not be inhibited from flashing during a pedestrian phase. Such an arrangement causes yellow trap.
   • Exception: When a railroad or drawbridge the FYA turns into pre-empts the signal, that FYA must be inhibited for entire phases, but never forced off while flashing.
   • The FYA must be controlled by the oncoming circular green, NOT a circular green facing the same direction the FYA faces.

     -- Exception: When no leg exists in the other direction (e.g. T intersection).

5. Only one lens of the Flashing Yellow Arrow signal face may be lighted at any one time.
6. The proper change intervals must be displayed on each signal face, as specified in the MUTCD:
   • The steady yellow arrow must accompany any change from flashing yellow arrow to red arrow.
   • The steady red arrow may follow the steady yellow arrow in the red change period.
   • The steady yellow arrow must not accompany any change from flashing yellow arrow to green arrow.
   • The flashing yellow arrow must continue to flash during the entire change interval before the phase with the green arrow.
   • The display on the flashing yellow arrow face must correspond to the display on the oncoming circular faces:

     FYA All-Arrow Face	Oncoming Circular Face	Condition
     Flashing Yellow Arrow	Steady Circular Green	Must change together
     Steady Yellow Arrow	Steady Circular Yellow	After Flashing Yellow Arrow
     Steady Green Arrow	Steady Circular Red
     Steady Yellow Arrow	Steady Circular Red	After Steady Green Arrow
     Steady Red Arrow	Steady Circular Red
     Any	No Oncoming Leg

7. The instructions for flashing yellow arrows in the manuals for the signal controller and conflict monitor must be strictly followed.

The signal must be checked for yellow trap:

Look for any case where a circular green is displayed in one direction while the oncoming traffic has only steady red and/or steady yellow indications.

Correctly Installed - Safe - No Yellow Trap

Yellow Trap from Wrongly Installed FYA

If the circular signals in the two images above are not synchronized, refresh this page or open it in a new tab.

Notice that the lower diagram turns all of the signals on the leading side yellow and then red simultaneously. This is the yellow trap. A left turning driver on the leading side is trapped. The correct installation (top) keeps the yellow arrow flashing until the oncoming circular green turns yellow.

The bottom image above simulates what happens when FYA is wrongly linked to the adjacent circular green instead of the oncoming circular green. It brings the wrong timing of left turns on circular green to the FYA, causing yellow trap. Notice the bottom diagram above has the same indications the diagram below has. Both cause yellow trap.

HOW LEFT TURNS ON CIRCULAR GREEN CAUSE YELLOW TRAP:

Yellow Trap from Left Turns on Circular Green

The problem is that the circular green controls too many movements to be used safely when left turns are controlled separately. It gives an indication to turn left permissively, as well as a go for straight-ahead and right turning traffic. This means that it can't be used as a left turn indication in a lead-lag signal.