Left-Turn Phasing—State-of-the-Art Review and the Outlook for Future Improvements

A Capacity Estimation Model for a Contraflow Left-Turn Pocket Lane at Signalized Intersections

“…Left turns are one of the most critical maneuvers at signalized intersections from both a safety and operations perspective ( 1 ). A 2010 U.S. Department of Transportation study analyzing crash factors found that the most common pre-crash event at intersections was a vehicle attempting to make a left turn (LT) ( 2 ); additionally, 17% to 32% of pedestrian crashes at intersections can be attributed to LT vehicles ( 3 ).…”

“…A model for signalized arterial travel time estimation capable of capturing the effect of queue spillback on link capacity found that the occurrence of link spillover can increase travel times by 50–100% for short distance links ( 7 ). Current best practices for mitigating the impact of queue spillover include longer turn bays and leading protected–permissive LT phasing ( 1 , 8 ). Thus, the development of signalized intersection treatments that maximize the number of vehicles serviced during LT protected phasing and minimize the likelihood that queue spillback will occur have the potential to greatly improve traffic flow at corridors with signalized intersections.…”