Since the early days of gap acceptance studies, time gap has been the prevailing measure adopted by researchers. With the advent of the true wide area detection technique - Video Image Processing (VIP), projected time gap, which is intuitively a better measure, has become available. In this paper, actual data for corresponding projected time gaps and conventional time gaps from CAMDAS - a VIP package by Australian Road Research Board - is compared to evaluate the performance of these two measures. Two aspects of measure performance are compared: (i) measure adaptability to different traffic conditions; and (ii) measure consistency. It is found that projected time gap is not only more consistent, but also adaptable to different traffic conditions. This study suggests that projected time gap should be adopted in future gap acceptance studies in order to better represent driver gap acceptance behaviors. (A*)
Abstract