DEVELOPMENT OF TRAFFIC MODELS BASED ON OBSERVED LINK FLOWS

Abstract

Origin-destination matrices play a fundamental role in transport planning and analysis as well as in traffic management. and control. However, their estimation by direct means such as interviews, license plate surveys and aerial photography is both time consuming and expensive as well as being unsuitable for on-line applications where the matrix is to be frequently updated. Therefore, indirect procedure based on observed link flows (traffic counts) and various forms of route assignment information have received much attention recently. Essentially, the estima- tion of O-D flows from traffic counts is the inverse process to that of assignment, whereby link volumes are estimated from a given O-D matrix. In the present study two models based on gravity model approach and Inouye's shadow cost concept of informa-tion minimisation approach have been developed to estimate an O-D matrix from traffic counts. Algorithm to find a solution to the model is then described. The models have been tested for a small network and results obtained from the model studies are not very well coinciding with those obtained from the observed values. Hence for further studies the improvement in accuracy of model should be given more emphasis.