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Latent demand—the activities and travel that are desired but unrealized because of constraints—have been historically examined from the standpoint of understanding the impacts of proposed capacity or service improvements on travel demand.

Drawing on work from a variety of theoretical perspectives, this paper presents a broader conceptual view of latent demand that provides a useful framework for researching and understanding these unmet needs. This is important from an equity standpoint, as it provides insights into to questions of transport disadvantage, social exclusion and poverty.

The framework presented here is theoretical in nature and untested empirically. This study aims to promote discussion and ultimately a more developed theory that can inform transportation planning and forecasting. A better definition and quantification of latent (or induced) demand can aid transportation planners to better predict the impacts of future transportation investments and other social, economic and technological changes.

Kelly J. Clifton is a professor of civil and environmental engineering at Portland State University. Dr. Clifton conducts research and teaches courses in various aspects of transportation planning and policy, including: travel behavior, land use and transportation, physical activity and health, and travel survey methods. She is the director of the Oregon Modeling Collaborative, a consortium of public and private agencies working to research, develop and apply integrated transportation modeling approaches. She is also a fellow in the Institute for Sustainable Solutions and the inaugural chair of the World Society for Transport and Land Use Research.