Observation of Gap Acceptance During Intersection Approach

This paper presents the results of a field test evaluating drivers’ decision making and gap acceptance for a left turn maneuver with opposite traffic; with a focus on the scenario where the turning vehicle is approaching the intersection. Twenty-three participants drove an instrumented vehicle ten times around an extended block turning left at four specific intersections. DGPS and radar data were combined to represent the trajectories of the turning vehicle and opposite traffic and to compute the gap between the turning vehicle and the lead vehicle of the on-coming traffic. The results cover the categorization of driver behavior based on the velocity profile while crossing the intersection. The velocity profile shows whether a driver stopped during the maneuver and the categories are defined based on where the driver stopped. The trajectories were then further sorted to account for the difference in speed profile or stopping location within one category. The characteristics of the accepted and rejected lags are presented and discussed, with an emphasis on turning drivers’ speed adaptation to the presence of an on-coming vehicle, and the presence of following traffic on a decision to stop. The conclusion of this study is that although valuable information was gathered during this field test, the data collection setup did not capture sufficiently the characteristic of the opposite traffic for a quantitative description of the effect of subsequent gaps on drivers’ decision to stop. Therefore, further data collection will be conducted on an instrumented intersection on a closed track.