The optimisation of traffic count locations in road networks

Origin-destination (OD) matrix estimation largely depends on the quality and quantity of the input data, which in turn depends on the number and sites of count locations. In this paper, we focus on the network count location problem (NCLP), namely the identification of informative links in the road network. Two extensions to previous methods of great practical relevance are presented. Firstly, a solution taking existing detectors into account (referred to as the second-best solution) is sought. This involves a reformulation of the optimisation problem and also the use of the original detector counts to update the link choice proportions. Secondly, the information content of the prior OD flows is (optionally) taken into account. The extended approach has been implemented in a software tool. The application of the tool to a network of moderate size is reported and its performance assessed.