ANALYTICAL WARRANT FOR SEPARATE LEFT-TURN PHASING.

The development of a new volume warrant for left-turn phasing at signalized intersections is presented. The concept is to maintain a fixed volume-to-capacity (V/C) ratio for all intersection movements. Thus left-turn phasing would be warranted when the unprotected left-turn V/C ratio exceeds that of through traffic. Left-turn capacity is derived from formulas in the Highway Capacity Manual and the Australian Road Research Board Capacity Manual. The warrant also combines both signal-timing and capacity-analysis procedures. The proposed warrant has been compared with other methods found in the literature and the results are, in general, favorable. This study is limited to four-legged intersections with one through lane and an exclusive left-turn lane of adequate length on all approaches. No adjustments for trucks, buses, or pedestrian interference are considered. It is understood that traffic signal parameters are selected according to Webster's optimum settings for fixed-time signals.