FLASHING YELLOW ARROWS
WHAT CAN GO WRONG?

If flashing yellow arrows are installed wrong or misunderstood, the following can go wrong:

PROBLEMS IN IMPLEMENTATION

  • Failing to prevent yellow trap.

    Yellow trap occurs when a permissive left turn ends while the oncoming straight ahead continues to flow:

    1
    Circular
    Greens
    2
    Signal
    Changes
    3
    Yellow
    Trap
    circular greens changes to yellow crash
  • Failing to prevent second yellow trap.

    Second yellow trap occurs when a permissive left turn ends while the oncoming right turn arrow continues to flow:

    1
    FYA Left
    Turns
    2
    2nd Yellow
    Trap
    3
    Next
    Phase
    circular greens with FYA second yellow trap next phase
  • Failure to prevent third yellow trap.

    Third yellow trap occurs when a flashing yellow arrow is ended when its parent phase is reserviced to answer a pedestrian call that does not allow the flashing yellow arrow:

    1
    FYA Left
    Turns
    2
    3rd Yellow
    Trap
    3
    Illegal
    Next Phase
    circular greens third yellow trap illegal next phase

    The reserviced phase is illegal only because it follows the flashing yellow arrow phase with no intervening all-red period for the straight-ahead movements.

FYA - WHAT IS CORRECT?

A table of whether or not pairs of flashing yellow arrow signal faces must be used on any one road.

WHAT IS CORRECT?
# Of
Legs
Intersection
Type
FYA Pairs
Required
3T-intersectionNO
3Preempted TYES
4One road is 1-wayNO
4One leg is 1-way awayYES
4Preempted one road 1-wayNO
4One leg is drivewayYES
4Both legs 2-wayYES
4Preempted 2-wayYES
4Offset straight road†1 each T
4Preempted offset†1 each T
>4FYA dangerous*NO FYA

*Other methods must be used to prevent yellow trap.

† An offset intersection is two T intersections very close together. The road that is not offset must have yellow trap protection if the first intersection is on the left, or if either intersection has a left turn signal.

Preemptions include emergency vehicle, railroad, drawbridge, and queue discharge. The proper design must be used to prevent yellow trap. Yellow trap must not occur during preemptions.

Intersection with 5 or more legs usually can't have permissive turns. Simultaneous multiple turns into or from the same leg, and multiple oncoming movements make permissive turns dangerous. Left turns must usually be protected or diverted, except if one leg is offset from the others.

PROBLEMS IN UNDERSTANDING

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