Updating Dynamic Origin-destination Matrices using Observed Link Travel Speed by Probe Vehicles

Abstract

A method for updating dynamic O-D matrix using observed link travel speed of probe vehicles is developed. The method consists of two parts: link flow of total traffic is estimated from the link travel speed of probe vehicles, and dy- namic O-D matrix is estimated using the estimated link flow and historical O-D matrix. The k-v function derived from the acceleration model by Gazis et al. (1961) is applied to the link flow estimate, and the entropy maximization model proposed by Willumsen (1984) is applied to the dynamic O-D demand estimate. By using Bayesian inference approach, the variance of the estimate as well as the point estimate of link flow is obtained. Also, the entropy maximization model is extended to incorporate the difference in the reliability of link flow estimates among links. The results of a case study show that the accuracy of the estimated dynamic O-D matrix is improved by the proposed method, and that the accuracy of the link flow estimates obtained in dynamic O-D demand estimation is im- proved by the proposed method, too.