An Algorithm for Determining Optimum Link Traffic Volume Counts for Estimation of Origin-Destination Matrix

Travel demand information is one of the most important inputs in transportation planning. Today, the access to origindestination(OD) matrix using traffic volume count information has caught the researchers’ attention because these methodscan estimate OD matrices based on the flow volume in the links of network with a high accuracy at a much lower cost overa short time. In such algorithms, the number and location of links are one of the main parameters for traffic volume count;hence a better OD matrix can be achieved by choosing the optimum links. In this paper, an algorithm is presented todetermine the number and location of optimum links for traffic volume count. The method specifies the minimum links tocover the maximum elements of OD matrix. This algorithm is especially useful for the estimation of ODM through gradientmethod, because only the O-D pairs covered by link traffic counts are adjusted and estimated in the gradient method. Thealgorithm is then scripted via EMME/2 and FoxPro and implemented for a large-scale real network (Mashhad). The resultsshow that about 95% of the ODM can be covered and then adjusted by counting only 8% of the links in the network ofMashhad.