Road infrastructure and demand induction

Based on available traffic counts, port statistics and statistics from bridge operators, the paper analyses the development in traffic before and after the opening of selected motorway sections and bridges in Denmark. The paper employs a screenline methodlogy where the total traffic flow across a long screenline is used to measure the development in aggregate demand in selected corridors. The paper analyses demand induction by establishing time series of aggregate demand that is compared with the national traffic index. Significant trend breaks in the association between aggregate demand in the corridors and the national index, following the opening of motorways or bridges, indicates demand induction by infrastructure expansion in a number of instances. Lack of significant trend breaks following opening year is found in peripheral areas where major population centres are missing. This indicates the necessity of some latent demand within suitable travel range for new infrastructure elements to produce significant amounts of induced demand. Estimates of demand induction as a percentage of the realised demand five years after opening are between 10% and 67% for new motorway sections depending on their location – and between 0% and 90% for bridges. The result for the bridges seem to depend strongly upon their location in the national transportation network.