Research Lead: Michael G. McNally
University: UC Irvine
Problem Statement: When a section of a transportation network is changed, typically in response to either current and/or forecast traffic congestion, it is relatively easy to estimate and (after project completion) to empirically measure the volume of traffic on the all sections of the network. A body of empirical evidence suggests that the majority of new capacity is in short time consumed. This leads to the common expression that states “you can’t build your way out of congestion” but such a quick conclusion belies the fact that more travel is being accommodated after capacity expansion, regardless of the resulting level of congestion. So what is this seemingly generated traffic and from where did it come? Many claim the generated traffic is induced demand, but a more nuanced characterization of the relationship between travel demand and transportation capacity is necessary to fully understand the dynamics of transportation system performance.
Project Description: This study will examine the objectives, assumptions, and system-wide impacts of congestion management strategies that reflect induced demand and pricing, as well as the underlying issues of social equity. Identified themes associated with the research include the measurement of economic, social, and environmental impacts of traffic congestion; the evaluation of potential strategies for improving congestion management; and the evaluation of the effects of congestion pricing on transportation and social equity. An exploratory approach will be taken and case studies will be identified in California where capacity enhancement has been completed and before/after data exists for corridor and regional performance and demographics. In addition to traffic performance, an assessment of travel behavior will utilize statewide travel surveys to identify the degree of stability in trip rates and travel time budgets as constraints on induced demand.
Status: In Progress
Project Partner(s): California Air Resources Board (CARB)