California Partners for Advanced Transportation Technology

Loop detectors are the preeminent vehicle detector for freeway traffic surveillance. Although single loops have been used for decades, debate continues on how to interpret the measurements. Many researchers have sought better estimates of velocity from single loops. The preceding work has emphasized post-processing techniques. Although rarely noted, these techniques effectively seek to reduce the bias due to long vehicles in measured occupancy and flow. This paper presents a different approach, using a new aggregation methodology to estimate velocity and reduce the impact of long vehicles in the original traffic measurements. Keywords: traffic surveillance, loop detectors, velocity estimation