A Study of Clearance Intervals, Flashing Operation, and Left-Turn Phasing at Traffic Signals. Volume 4. Left-Turn Phasing

摘要

This volume describes a study to develop recommendations concerning the utilization of the protected/permissive left turn phasing technique. The study procedures included a literature review, a review of state laws, questionnaires to public officials and to drivers, and field studies. The protected/permissive left turn phasing technique was found to improve traffic movement efficiency and operations where left turn phasing is not needed at all times during the day. It was also determined that an increased level of public understanding of the meaning of left turn signal indications, the arrow versus the green ball, is needed before general recommendation for usage can be justified. Precautions in the use of the technique are also included.