Evaluation of Methods for Pedestrian Safety Improvement on Left-Turning Vehicles Movement in Intersections

Warning systems are developed for left-turning vehicles at intersections where protected left-turns are not warranted or cannot be provided, due to limitations of right of way or intersection capacity. These are meant to provide warnings to left-turning vehicles of the approaching vehicles from the opposite direction, when the time to turn deems unsafe. To implement such systems, real time estimation of the probability of vehicle conflict is necessary. A study has been conducted using video and radar at various intersections, to obtain estimates of turning time and acceptable gaps for drivers under various situations. Initial pilot observations indicate that the presence of pedestrians in intersections had an immediate and substantial impact on the movements of left-turning vehicles. From a preliminary systematic video analysis, in the presence of pedestrians on the destination crosswalk, the mean and standard deviation of both the gap and gap components (i.e., turning time and the “buffer” between the turning vehicle and the next oncoming vehicle) increases. On the basis of these observations, pedestrian-detection mechanisms would be useful for such intersection warning systems with a threshold for warning that is adjusted for pedestrians when they are present or in the vicinity of the destination crosswalk.