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Protected Left Turn Signal Phase

What is it?


A protected left turn signal phase provides the motorist a period of time where

left turns can be made without encountering conflictingvehicular and pedestrian movements.

Left turn signal

When are they used?

  • where left turns are permitted from two lanes on one approach and there is an opposing through movement
  • where the left turn traffic queue frequently extends beyond the left turn lane, thus blocking the through movement
  • where a significant left turn volume is present during peak traffic hours
  • where intersection geometry creates a visibility problem which may be alleviated by a left turn phase
  • where the speed of approaching traffic is sufficiently high to make driver judgement of gaps difficult

What are the issues?

Motorists naturally feel more safe making a left turn with an arrow. However, in many cases, the turning capacity provided by gaps in oncoming traffic plus the amber signal phase can safely accommodate left turns at an intersection.

The careful design of a phasing plan for a signalized intersection is essential to its safe and effective operation. Unwarranted signal phases create undesirable effects in terms of stops, vehicular delay and increased fuel consumption.