Calibration and Validation of Capacity Analysis Procedures for Left Turn Lanes in Illinois

摘要

Phase I of the research study has two principal objectives: (1) Provide local calibration values for saturation flow rates for exclusive, dual left-turn lanes (EDLTL) in large urban areas in Illinois; and (2) Develop delay-based guidelines for converting exclusive single to dual left-turn lanes (ESLTL to EDLTL) in urban areas in Illinois. Field data was gathered at nine sites in the Chicago Metropolitan area. These indicated that the average saturation flow rate for dual left-turn lane was 1831 vph/lane. The study also found a lane differential effect on saturation flow rate with the median lane having a saturation flow rate of over 1900 vph. Delay models have been established for the critical left turn and opposing through movements for both ESLTL and EDLTL configurations. Delay models are espressed in terms of total intersection critical value and subject street critical volume. A graphical form of the guidelines is also given.