Left-Turn Treatments at Intersections

TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 225: Left-Turn Treatments at Intersections will be of interest to traffic engineers in both the public and private sectors, as well as to design engineers, safety and law enforcement officials, traffic signal technicians, and others concerned with the accommodation of nonmotorized transportation ( pedestrians and bicycles) on the roadway. The synthesis describes the traffic conditions, signalization, signing, and geometric design issues associated with accommodating left-turning vehicles at intersections. This report of the Transportation Research Board discusses the basic concerns related to left-turn movements and the guidelines and requirements for handling these movements in the traffic stream. It also addresses the design criteria for left-turn treatments and the performance measures frequently applied to determine their effectiveness. The synthesis discusses the specific requirements for signing and pavement markings, and the various elements of traffic signal requirements, signal design and installation, phasing optimization, and lane-use controls. There is also a description of special applications such as U-turn control, pedestrian requirements, bicycles, and light rail transit interface.