University of California Transportation Center

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 stimulations. 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.