This project develops and presents easy-to-use guidelines for selecting the "best" left-turn treatment to implement at a signalized intersection. The information contained in this report is based on a synthesis of current research and the operational experiences of over 200 practicing traffic engineers. Alternative left-turn treatments range from separate turning lanes to complex signal phasing schemes. This Implementation Package will aid in the design and application of these treatments. Widespread use of its contents will significantly improve both operation and safety aspects at signalized intersections. The traffic signal engineer can use these guidelines to either justify or deny the request for a left-turn treatment at a signalized intersection. For some cases, no firm indication of need may be present and the decision maker will still have to use engineering judgement. The traffic engineer should remember that these guidelines are an aid for decision making--not the decision. The guidelines include various types of left-turn phases. The considerations (including advantages and disadvantages) of a number of phasing schemes are covered. Signal displays are also discussed. Attention is given to the capacity, fuel consumption, operational, and safety trade-offs of the types of left-turn treatments. Finally a specific set of guidelines are presented for day-to-day use by the traffic engineer. The guidelines are not intended to encourage left-turn phases but only to discuss considerations and options where their use is being considered. (Author/publisher)
Abstract