November 13, 2009


Trip-Generation Rates Spreadsheet for Smart-Growth Land Use Projects in California: the Need and the Context


The California Environmental Quality Act (CEQA) and other laws and ordinances require the potential transportation effects of new development to be analyzed in a Traffic Impact Analysis (TIA). The first step in the TIA process is to estimate the number and types of trips associated with the proposed project – its “trip-generation.” For over two decades, analysts have relied heavily on trip generation rates compiled by the Institute of Transportation Engineers (ITE). For a variety of reasons, analysts often inappropriately apply unadjusted suburban ITE rates in areas in areas where transit, walking and biking are viable modes. In these instances, automobile traffic is overestimated, and infrastructure planning and funding decisions are distorted toward the auto and away from alternative modes.

This presentation provides an overview of the context and approach of a recently launched project at UC Davis that is sponsored by the California Department of Transportation (Caltrans). The project aims to develop a technically sound and operationally straightforward method for appropriately estimating trip generation for “smart growth” land use projects, such as: urban and suburban infill, transit-oriented development, as well as clustered and mixed land uses. The presentation will address how and why TIA and trip generation are performed in the manner that they are. It will then describe the approach being taken and the challenges faced by the Caltrans/UCD project team in creating a more environmentally sensitive and realistic approach to the estimation of project trip generation.

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