A low cost experimental procedure is presented for videotaping vehicle tracking data at a given roundabout location. These data are examined frame by frame to extract individual vehicle position and time as it progresses along its path. Accuracy of the traffic estimates are established by comparing vehicle speed profiles from the vehicle tracking data with speed profiles obtained independently using a radar speed gun at the same roundaboutlocation. The vehicle tracking data was used to estimate safety performance at different segments of the roundabout using different indicators, such as, time to crash, deceleration rate to avoid the crash, crash potentialindex that incorporates the braking capability of individual vehicles, number and exposure time in conflict. Differences in safety performance arediscussed with respect to the type of indicator used, assumed traffic inputs and differences in roundabout geometry. The results of this study provide meaningful experimental indicators of potential real-time safety problems at different roundabout locations subject to behavioral driver responses to different traffic conditions.
Abstract