Trunk roads and the generation of traffic

the long version

The opening of the M25 motorway (freeway) around Greater London in the late 1980s resulted in traffic volumes that far exceeded forecasts. The British government commissioned this study to determine whether the construction of new major roads results in additional trips that were not being made previously. The report concluded that in congested areas there are many extra trips that people would make if their routes were faster. The report cautions that releasing this pent-up demand in one area could cause problems in other parts of the roadway system, and suggests some ways to quantify the latent demand.