Estimation of Origin-destination Matrices from Link Counts



Estimation of Origin-destination Matrices from Link Counts

Authors

GORDON, A, Mott MacDonald, UK; HAZELTON, M, University of Western Australia, Australia; WATLING, D, University of Leeds, UK

Description

An accurate origin-destination trip matrix is an essential part of a successful traffic assignment model.
Typical methods for building a matrix involve expensive surveys which often have low sample rates and
rarely observe all possible OD movements.

Abstract

An accurate origin-destination trip matrix is an essential part of a successful traffic assignment model.
Typical methods for building a matrix involve expensive surveys which often have low sample rates and
rarely observe all possible OD movements. Although there are well-established techniques for
estimating trip matrices from link counts they depend on having a prior trip matrix, the accuracy of
which is a key determinant of the accuracy of the estimated matrix.

This paper describes a method developed as part of a project for the UK Highways Agency which can
estimate a trip matrix from link counts alone, without the need for a prior matrix. It does this by making
greater use of the information provided by counts collected over a number of days. Rather than
working with just mean counts, the variance and the covariance of counts are also used. In many cases
this provides enough information to estimate route flows using a least squares estimator, from which OD
flows are readily obtained. The information from the link counts can be supplemented with estimates of
route choice proportions.

The paper describes the theory of the method in detail and presents the results from two applications to
UK road networks. The first uses simulated data on a section of the M25. The second involves real
data from automatic traffic counts on the Kent trunk road network. These and other results lead to
conclusions about the optimal application of the method, including issues such as the number of days of
count data required.

Publisher

Association for European Transport