The costs of congestion in the Netherlands. In this paper we have presented an economic theory based approach to quantifying congestions costs, which lead us to argue that the total costs of congestion include two components: observed costs and unobserved costs. The first can be measured directly on the road network, the second relate to travel behaviour that has been modified in reaction to the congestion. Our analysis has suggested that in networks with substantial and persisting congestion, the unobserved costs can be quite important relative to the observed costs. Estimates of congestion costs in different countries differ widely in terms of methods and results, but they only address observed costs. Issues in measuring congestion costs are: costs compared to which situation (optimal pricing or free-flow)? Which methods are appropriate? and: Should unobserved costs be included ? Using the Dutch National Model System we have quantified the year 2000 congestion costs. We have used two methods, a more traditional speed-flow based approach, and a more comprehensive logsum based approach that included unobserved effects (choice of mode, destination, and timing of travel). The results indicated that the second approach arrives at a total congestion costs estimate almost twice as high as the first approach. This can be seen as empirical support for the “unobserved costs” theory. (Author/publisher)
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