Link travel time and delay estimation using transit AVL data

Estimating arterial link travel times and traffic delays using vehicular positioning data, such as automatic vehicle location (AVL) data, is still a challenging subject. The difficulties exist in allocating the travel time between two consecutive AVL reports of a vehicle to each traversed link, especially when the data sampling frequency is low, and identifying the proportion of traffic delay in link travel time. In this paper, transit buses with 30-second sampling interval AVL data were applied as probes to estimate link travel time and traffic delay caused by intersections or alighting and boarding at bus stops. The estimation model proposed in this paper decomposed travel time into three components: free flow travel time, congestion time, and stopping time at signalized intersections and bus stops, then allocated them to each road link. Unlike existing deterministic methods, the proposed solution defined a likelihood function that is maximized to solve for the most likely traffic delays for each road segment on the route. Field tests were conducted on a typical arterial corridor in Edmonton, Canada for data collection and algorithm performance evaluation. The results suggested that the proposed model provides effective and accurate estimation of traffic delay, which can be further applied to transit based or probe vehicle based traffic applications, such as travel time estimation and travel speed estimation.