Analysis of Trends Underlying Urban/Regional Impacts of Traffic Growth

Abstract

National and state data verify that the growth of highway vehicle traffic exhibits self-limiting characteristics (travel and population growth rates are becoming more and more similar due to saturation of the automotive market). However, the implications of these characteristics for delays at the regional or metropolitan level depend on changing trip lengths and spatial distributions. To avoid treating all regional travel growth the same, as do current national policies, four scenarios are examined: uniform travel growth, random travel growth, growth in congested areas, and growth in uncongested areas. The scenarios are tested using an Urban Transportation Planning System–based model modified for this study. The scenario analyses indicate widely varying manifestations of increased travel on delay. They suggest that policies that treat all travel growth the same might be more effective if modified to reflect underlying trends and alternative planning strategies.