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 preliminary in nature; its scope 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. Finally, it is understood that traffic signal parameters are selected according to Webster's optimum settings for fixed-time signals.

'!'he provision of separate J. ert-turn phasing at intersections has been the subject of considerable research. The need for developing guidelines for left-turn phasing sterns from an absence of uniform criteria in the Manual on Uniform Traffic Control Devices (MUTCD)(1) and the need to formulate consistent policies regarding left-turn treatments at signalized intersections. The majority of left-turn warrants follow these general criteria: