The traffic effects of fixed links: Short and long-run forecast accuracy

Abstract

Economic and financial appraisals of road projects depend on reliable traffic forecasts, and there is a need for knowledge of how traffic reacts to changes in the transport network. In the article, the authors study the effects on traffic of fixed links constructed in Norway and the extent to which planners have been able to forecast those effects with an acceptable degree of accuracy. The main finding is a substantial underestimation of traffic in the long term. Initially, the differences between the forecast traffic and actual traffic were relatively small, but the differences increased over time. In the long term, actual traffic might be twice as high as the forecast traffic. This finding deviates substantially from findings from other countries, where overestimation of traffic on tolled, at least in the short term, seems to have been the norm.