Estimation of an O-D Matrix from Traffic Counts – A Review.

Following a review of conventional methods,for estimating a trip matrix,the possibility of using cheaper methods based on traffic counts is discussed. Three broad groups of models for such estimation have been identified. The first one assumes that trips follow a gravity type pattern and the problem is reduced to calibrating the parameters of such a model from the observed counts. Depending on the assumed form of the gravity model this technique leads to linear or non-linear regression solutions. The second group of models attempts to estimate the 0-D matrix through a network equilibrium approach based on Wardrop's first principle. The third group follows an entropy maximising approach in which the most likely trip matrix compatible with the observed flows is sought. Finally, the advantages of each approach are discussed and the most promising technique and areas of application are identified.