Generation Matters: An Integration of Cohort Analysis & Travel Demand Modeling

By Dr. Sarah Bush, Assistant Professor, Southern Utah University

Abstract
Over the next 30 years, the Boomers will double the 65+ population in the United States and comprise a new generation of older Americans. This study forecasts the aging Boomers' travel. Drawing on the theory of generations, this study investigates empirically whether cohort differences in travel exist between the Boomers and the current 65+ population. It incorporates theoretically motivated cohort variables related to the historical processes of motorization and gender role evolution. The resulting forecast predicts the aging Boomers' travel demand with respect to activities requiring travel, person miles traveled, usage of transit and non-motorized modes, and trip chaining propensity. Data extracted from the 1977, 1983, 1990, and 1995 National Personal Transportation Surveys (NPTS) are used to estimate discrete and joint discrete/continuous demand models. Multiple imputation is used to impute missing survey data. Iterative proportional fitting is used to simulate future populations. In the estimated models, the cohort variables are significant, and cohort variable inclusion increases forecasted travel. The implication for transportation modeling is that historical location and generation membership affects transportation behavior. The implication for planners is that in preparing for future 65+ transportation needs, studying the current 65+ population is not adequate. The Boomers will comprise a new generation of 65+ with different associated travel needs.

About the Speaker
Dr. Sarah Bush is an Assistant Professor at Southern Utah University with a dual appointment in Integrated Engineering & Construction Management. She is currently developing a professional masters program in real estate and land development. She has worked as a Project Manager for Skanska USA Building and the Congress Group, a private Boston development company. She completed her doctoral work at MIT in 2003 under the supervision of Prof. Moshe Ben-Akiva and Dr. Joseph Coughlin, and recently received the Eric Pas Dissertation Prize from the International Association of Travel Behavior Researchers.