Estimation of Congestion Costs in the Netherlands
E Kroes, RAND Europe; C Koopmans, SEO, University of Amsterdam, NL
Traffic congestion costs money and welfare. The first initiative to quantify monetary costs in the Netherlands goes back to the late 1970?s, when estimates were made commissioned by the ?road lobby?. The method was simple: estimate total queue length throughout the year, and multiply this by the estimated average delay per kilometer queue and value-of-time to obtain annual congestion cost. Since then more accurate estimates have been obtained, reported annually by the Dutch Ministry of Transport, but essentially the method has not been changed. The key assumption behind it is that observed queues allow us to accurately estimate the total disutility caused by the traffic congestion.
In this paper we explain why behavioral changes induced by congestion, like other timing of travel, changes in mode choice, destination choice and in other decisions made by (potential) travellers, are also a part of the costs of congestion. As the time delays on roads get worse, one might expect more and more behavioral changes. In such situations, the observed delays may seriously underestimate the true congestion costs. This is relevant both for ex-ante economic evaluations, using prediction models, and ex-post evaluations, using observed congestion. We shall illustrate the magnitude of a number of possible effects by using simulation results from the Dutch National Model System. We shall also describe how better ex-ante evaluations can be obtained by means of relatively simple modifications of existing software.
This paper is, of course, not unrelated to the discussions that have taken place in the context of the SACTRA report. We do not claim to come up with something entirely new. The practical relevance, however, is that several European countries, including The Netherlands but also for instance Sweden, are currently reviewing or extending their formal economic evaluation framework, and we feel that our paper might contribute to the improvement of the current state-of-practice.
Association for European Transport