GUIDELINES FOR PROTECTED/PERMISSIVE LEFT-TURN SIGNAL PHASING

Guidelines for the use of protected/permissive left-turn signal phasing were developed by collecting and analyzing data on traffic and roadway conditions for protected-only, protected/permissive, and permissive left-turn phasings to identify relationships among these conditions and signal phasings. The following left-turn signal aspects are addressed: (a) traffic volume based on the peak-hour minimum left-turn volume and the product of the peak-hour left-turn and opposing volumes with lower and upper limits, (b) annual left-turn accident experience based on the critical number and rate, (c) left-turn traffic conflict experience based on the critical number and rate, (d) left-turn delay, (e) site condition, (f) user cost savings for protected/permissive versus protected-only left-turn phasing, and (g) traffic engineering judgment.