right-hand traffic Left-hand traffic (LHT) and right-hand traffic (RHT) are the practices, in bidirectional traffic, of keeping to the left side or to the right side of the road, respectively. They are fundamental to traffic flow, and are sometimes referred to ...

, the yellow trap is a potentially dangerous scenario in traffic flow through a

traffic light Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at intersection (road), road intersections, pedestrian crossings, and other locations in order to control flows of traf ...

relating to permissive left turns. It occurs when a circular yellow light is displayed to a movement with permissive left turns, while at the same time, opposing through traffic still has a circular green light. Some drivers facing the circular yellow (then red) lights will assume the opposite direction faces the same color display, and that oncoming traffic will stop. This leads to potential traffic conflict if drivers attempt to complete a left turn when it is not safe to do so. The left-turning driver may legally be at fault, for failure to yield, but made an understandable mistake. Solutions to the yellow trap include the flashing yellow arrow, Dallas phasing, Arlington phasing, simultaneously ending both through movements (circular green lights change to yellow, then red) before serving both left-turn movements (green arrows), or prohibiting one of the two left-turn movements. Many agencies in North America routinely allow the yellow trap, especially during emergency vehicle preemption, despite clear prohibition from the

Manual on Uniform Traffic Control Devices The ''Manual on Uniform Traffic Control Devices for Streets and Highways'' (usually referred to as the ''Manual on Uniform Traffic Control Devices'', abbreviated MUTCD) is a document issued by the Federal Highway Administration (FHWA) of the Unit ...

. The MUTCD allows this sequence only if a sign reading Oncoming Traffic Has Extended Green or Oncoming Traffic May Have Extended Green is posted. Some of this stems from difficulties programming older traffic signal control software to prevent the yellow trap, but much stems from traffic engineers or technicians not understanding the yellow trap hazard, or believing it is not a serious problem. In left-hand traffic, the same scenario is applicable for drivers turning right.

References

External links

{{Wiktionary, yellow trap
Fixing the Yellow Trap
Kittelson & Associates.

from the

.
Yellow Trap Index Page
midimagic.sgc-hosting.com Traffic signals