The Case for Moderate Growth in Vehicle Miles of Travel: A Critical Juncture in U.S. Travel Behavior Trends

This report hypothesizes that the United States has reached a critical juncture in terms of national mobility trends and underlying socio-demographic conditions and travel behavior that will result in more moderate rates of annual vehicle miles of travel (VMT) growth in the future. However, slower VMT growth may not portend lower rates of congestion growth. This report explores the major factors that influence travel behavior. The indirect factors are discussed first using primarily empirical data. These are divided into three major categories: socio-economic conditions, land use conditions, and transportation system conditions. This report concentrates most on the role of the socio-economic conditions and travel behavior followed by a discussion of the direct factors. Several of these factors appear to be undergoing historic trend reversals. In addition, new evidence suggests that congestion levels have reached the point where average travel speeds are declining. This declining speed may provide additional dampening of VMT growth. Two forecasts of future VMT are produced that build on the data and information presented in the body of the report. This report is intended to stimulate thinking about the future trends in travel demand and the underlying factors that influence those trends.\n