The design of traffic management schemes usually requires knowledge of the pattern of trips on the system under scrutiny. This pattern is ordinarily described by an origin-destination (O-D) flow matrix. One common task of this type of matrix is the estimation of flows between the intersection approaches on a stretch of road. Estimation is based on intersection flow counts that are supplemented by a license-plate survey. In this paper a procedure is developed to obtain the most likely O-D flow estimates by using both intersection counts and results of the license-plate survey. The procedure is described in detail on the basis of a numerical example. An earlier paper reported a method of estimation that relies on intersection counts only and does not require the conduct of a sample license-plate survey. An empirical examination is conducted to test how estimation accuracy increases when the added information from the license-plate survey is used. This examination reveals that when the supplementary license-plate survey is small, the maximum-likelihood method yields unsatisfactory estimates. This efficiency is rectified by the use of a Bayesian method. The resulting solution procedure is simple, and satisfactory estimates are produced. (A)
Abstract