Citation

Heanue K. Transp. Res. Circular 1998; (481): 33-45.

Copyright

(Copyright © 1998, U.S. National Academy of Sciences Transportation Research Board)

DOI

unavailable

PMID

unavailable

Abstract

This paper objectively addresses the induced travel issue by answering the following questions: First, if new highway capacity does indeed "induce" new travel, to what extent compared to other factors? Second, if new highway capacity (as one of many factors) induces new travel, how should induced traffic be accounted for in the objective evaluation of highway investments? For the purposes of this paper, induced travel is defined as any increase in daily travel (measured as passenger or vehicle miles of travel) resulting from a change in the transportation system. It is concluded that the role of highway capacity expansion in increasing highway travel has been small relative to other factors. Highway capacity expansion interacts with far more important variables such as population, household and employment growth, personal income and auto ownership increases, regional economic growth and fuel price changes as determinants of total travel demand. Planning processes must have the capability to objectively examine a thoughtful combination of strategies to assure that, while the population of a region grows, its access and mobility needs are sustained and its environmental quality is enhanced. Metropolitan areas are encouraged to consider combinations of synergistic strategies, including: balanced investment, covering both capacity expansion and better system operation and management for all modes; alternative urban forms and urban design; and appropriate pricing to maximize transportation system efficiency. The major determinants of travel demand are clearly socio-economic in nature. However, the inducement of travel due to any transportation system change is an issue that needs to be and can be addressed by considering behavioral and land use change mechanisms.