The Ethical Challenges and Professional Responses of Travel Demand Forecasters
AbstractThirty 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 such forecasts are systematically optimistic -- often wildly so -- for reasons that cannot be explained solely by the inherent difficulty of predicting the future. Why do modelers -- professional engineers and planners who use quantitative techniques to predict future demand for travel and estimate its potential impact on built and proposed transportation facilities -- generate biased forecasts and otherwise tolerate the misuse of their work? On initial consideration, it is tempting to surmise that corrupt modelers are responsible for biased forecasting. Indeed, corruption is the most common explanation of forecasting bias and tales of mercenary behavior are all too common in the field. Data from in-depth interviews with twenty-nine travel demand forecasters throughout the United States and Canada, however, suggest new and different ways to understand the suspect behavior 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 practictioners 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. This disillusion wish not to see that they do not matter and the complacent that they do. Bias and misuse seem to be the unintentional byproducts of these attitudes. Beyond enhancing the understanding of the systemic failures of travel demand modeling, this research suggests practicable steps to reform and outlines an agenda for future work. Attention to these matters is important, not just to avoid expenditures on projects and programs that cannot be justified on the basis of sound utilitarian calculations, but also to restore and preserve the credibility of a profession.
Download InfoIf you experience problems downloading a file, check if you have the proper application to view it first. In case of further problems read the IDEAS help page. Note that these files are not on the IDEAS site. Please be patient as the files may be large.
Bibliographic InfoPaper provided by University of California Transportation Center in its series University of California Transportation Center, Working Papers with number qt7vb2d17h.
Date of creation: 01 Sep 2003
Date of revision:
Contact details of provider:
Postal: 109 McLaughlin Hall, Mail Code 1720, Berkeley, CA 94720-1720
Web page: http://www.escholarship.org/repec/uctc/
More information through EDIRC
Social and Behavioral Sciences;
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:
- A. P. Thirlwall, 1983. "Introduction," Journal of Post Keynesian Economics, M.E. Sharpe, Inc., vol. 5(3), pages 341-344, April.
- Mackett, Roger L. & Edwards, Marion, 1998. "The impact of new urban public transport systems: will the expectations be met?," Transportation Research Part A: Policy and Practice, Elsevier, vol. 32(4), pages 231-245, May.
- Skamris, Mette K. & Flyvbjerg, Bent, 1997. "Inaccuracy of traffic forecasts and cost estimates on large transport projects," Transport Policy, Elsevier, vol. 4(3), pages 141-146, July.
- Mackie, Peter & Preston, John, 1998. "Twenty-one sources of error and bias in transport project appraisal," Transport Policy, Elsevier, vol. 5(1), pages 1-7, January.
- Rubin, Thomas A. & Moore II, James E. & Lee, Shin, 1999. "Ten myths about US urban rail systems," Transport Policy, Elsevier, vol. 6(1), pages 57-73, January.
- Goetz, Andrew R. & Szyliowicz, Joseph S., 1997. "Revisiting transportation planning and decision making theory: The case of Denver International Airport," Transportation Research Part A: Policy and Practice, Elsevier, vol. 31(4), pages 263-280, July.
- Tore Langmyhr, 2000. "The Rhetorical Side of Transport Planning," European Planning Studies, Taylor and Francis Journals, vol. 8(5), pages 669-684, October.
- Nelson, Robert H, 1987. "The Economics Profession and the Making of Public Policy," Journal of Economic Literature, American Economic Association, vol. 25(1), pages 49-91, March.
- Tal, Gil & Cohen-Blankshtain, Galit, 2011. "Understanding the role of the forecast-maker in overestimation forecasts of policy impacts: The case of Travel Demand Management policies," Transportation Research Part A: Policy and Practice, Elsevier, vol. 45(5), pages 389-400, June.
For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (Lisa Schiff).
If references are entirely missing, you can add them using this form.