Left-turn movements at intersections, including drivewaysespecially movements that are made from lanes that are shared with through trafficcause delays and adversely impact safety. Although left-turn warrants have been updated, many agencies still use research performed by M. Harmelink from the mid-1960s. While most states use procedures that are based on Harmelink, a number of limitations of Harmelinks procedure have been identified. Economic analysis can provide a useful method for combining traffic operations and safety benefits of leftturn lanes to identify situations in which left-turn lanes are and are not justified economically. This project used a benefit-cost approach to determine when a left-turn lane would be justified. The steps included simulation to determine delay savings from installing a left-turn lane, crash costs and crash reduction savings determined from safety performance functions and accident modification factors available in the Highway Safety Manual, and construction costs. Left-turn lane warrants were developed for rural two-lane highways, rural four-lane highways, and urban and suburban roadways. In addition, warrants for bypass lanes were developed for rural two-lane highways. A Design Guide on Left-Turn Accommodations at Unsignalized Intersections was developed that discusses left-turn lane designs, traffic control treatments, and case study examples.


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    Title :

    Development of Left-Turn Lane Warrants for Unsignalized Intersections


    Contributors:
    K. Fitzpatrick (author) / M. A. Brewer (author) / J. S. Gluck (author) / W. L. Eisele (author) / Y. Zhang (author)

    Publication date :

    2012


    Size :

    270 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English




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