Thirty years ago scholars first presented convincing evidence that local officials use biased travel demand forecasts to justify decisions based on unstated considerations. Since then, a number of researchers have demonstrated convincingly that travel demand forecasts are systematically optimistic - often wildly so - for reasons that cannot be explained solely by the inherent difficulty of predicting the future. Why do modellers generate biased travel demand forecasts and tolerate the misuse of their work? Data from in-depth interviews with twenty-nine travel demand forecasters throughout the United States and Canada suggest new ways for understanding the suspect behaviour of transportation planning professionals. Those most likely to introduce bias and invite misuse of travel forecasts assume that their technical analyses have little, if any, impact on policy making. For many, this leads to disillusionment and requires responses to cope with feelings of marginalization. Others, untroubled by their apparent lack of influence, are complacent and need ways to avoid the ethical questions of practice. Both types of practitioners circumscribe professional roles and rely on the self-deceptive strategies of evasion and excuse making to mute their own disquieting realities that undermine positive concepts of self. The disillusioned wish not to see that they do not matter and the complacent that they do. Bias and misuse seem to be the unintentional by-products of these attitudes. For the covering abstract see ITRD E128680.
Abstract