Abstract
An empirical study was conducted to quantify the impact of several variables on driver left-turn gap acceptance behavior. These variables included gap duration, the driver's wait time in search of an appropriate acceptable gap, the time traveled by a driver to clear a conflict point, and the rain intensity. Gap acceptance data for a permissive left-turn maneuver at a signalized intersection were collected over a 2-month period. Logistic regression models calibrated to the data reveal that the acceptable gap duration decreases as a function of the driver's wait time and increases as the rain intensity increases. The study then demonstrates how the critical gap is influenced by a number of parameters, including the wait time and rain intensity, and also demonstrates how rain intensity affects the permissive left-turn saturation flow rate. It is anticipated that these findings can be used to develop weather-specific traffic signal timings that account for changes in traffic stream saturation flow rates due to changes in critical gap values as a function of weather conditions.