USE AND EFFECTIVENESS OF DOUBLE LEFT-TURN MOVEMENTS

Double left-turn movements can effectively accommodate large volumes of left-turn traffic. A thorough study of signal timing and phasing needs, intersection and roadway geometrics, signing and marking requirements, etc., must precede and influence the design of double left-turn facilities. No common practice is being used for the type width and pattern of longitudinal markings for double left-turn lanes, and the effect of variances is unknown. The development of national guidelines for double left-turn movements would be helpful. Suggestions are offered to those who would consider the installation of a double left-turn movement.