Induced Demand: An Urban and Metropolitan Perspective Robert Cervero, Professor Department of City and Regional Planning University of California Berkeley, California E-Mail:
[email protected] Paper prepared for Policy Forum: Working Together to Address Induced Demand U.S. Environmental Protection Agency Federal Highway Administration, U.S. Department of Transportation Eno Transportation Foundation, Incorporated March 2001 Second Revision Induced Demand: An Urban and Metropolitan Perspective Most studies of induced travel demand have been carried out at a fine to medium grain of analysis – either the project, corridor, county, or metropolitan levels. The focus has been on urban settings since cities and suburbs are where the politics of road investments most dramatically get played out. The problems assigned to induced demand – like the inability to stave off traffic congestion and curb air pollution – are quintessentially urban in nature. This paper reviews, assesses, and critiques the state-of-the-field in studying induced travel demand at metropolitan and sub-metropolitan grains of analysis. Its focus is on empirical and ex post examinations of the induced demand phenomenon as opposed to forecasts or simulations. A meta-analysis is conducted with an eye toward presenting an overall average elasticity estimate of induced demand effects based on the best, most reliable research to date. 1. URBAN HIGHWAYS AND TRAVEL: THE POLICY DEBATE Few contemporary issues in the urban transportation field have elicited such strong reactions and polarized political factions as claims of induced travel demand. Highway critics charge that road improvements provide only ephemeral relief – within a few year’s time, most facilities are back to square one, just as congested as they were prior to the investment.