The Effects of Forecasts on the Level of Motorization – A Self-fulfilling Prophecy?

Anna Mayerthaler, Harald Frey, Ulrich Leth

Last modified: 2017-02-28


Besides the population growth, the level of motorization is an essential factor influencing forecasts on transport demand carried out with transport models. Results of such models are often used in transport planning for example to scale planned road infrastructure. Looking at the development of the level of motorization in the past, it becomes apparent that permanent transgressions of the prognoses have taken place. As a consequence the everincreasing levels of motorization were treated as “law of nature”, resulting in upward corrected prognoses. In the last decade this trend seems to be reversed. We present that in many countries worldwide the levels of motorization are stagnating or even decreasing. Especially in cities this development is obvious, showing the influence of transport policies on vehicle ownership. The common transport models did not predict this development. Additionally the strong influence of the level of motorization on the forecasts of transport behaviour is shown, based on two different scenarios. One of the scenarios is mapping the influence of transport and land-use policies on the level of motorization. In the second scenario the assumed growth of the level of motorization is fed externally into the model, therefore not being influenced by policy measures.


level of motorization; transport demand models; prognoses

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