Induced Traffic: Review of the explanatory models

A common claim in transport planning is that more road capacity generates additional car travel. While most authors argue that this additional traffic reflects an increase in the consumer surplus of the travellers, others see these additional trips and miles as wasteful. The induced traffic demand from increased infrastructure supply over time typically coincides with an increase in population and a higher per capita income in the study area. To isolate the effects of the different variables is a complicated task. There is also a danger of oversimplification in answering this complex problem. This occurs quite frequently during discussions of traffic growth. The present paper starts by exploring the concept of induced traffic, after which the major methodologies currently in use are analysed and discussed. The focus of the review is the various econometric models and approaches, as well as their results. Published findings reviewed here show an elasticity of daily vehicle mileage on lane miles for the short and long run of 0.2 – 0.3 and 0.6 – 0.8, respectively. The paper concludes by suggesting central considerations for future work.