Smart Growth Trip Generation
Objective: The goal of this project is to develop and disseminate data and a method that practitioners can use to estimate multimodal trip-generation rates for “smart growth” land use development projects proposed in California. These include projects located in downtowns and other urban areas served by transit service and in which a variety of land uses are close enough to allow walking or bicycle travel. An acceptable method is needed to estimate trip-generation for transportation impact analyses/studies of “smart growth” projects, which agencies typically require to estimate the impacts of proposed projects and identify improvements to help “mitigate” impacts.
Need: The first step in preparing a transportation impact analysis is to estimate the number of trips by cars, trucks, and other modes of travel that may result from a proposed land use project – which is commonly referred to as “trip-generation.” Currently, practitioners typically obtain trip-generation rates published by the Institute of Transportation Engineers (ITE), a national professional organization. This data is collected primarily at suburban sites without significant transit, bicycle, or pedestrian facilities and is available only for vehicles, not for “active” modes such as walking, bicycling, or transit. However, recent studies indicate that such data often significantly over-estimates the number of trips from cars and trucks for land use projects located in urban areas near transit and within easy walking distance of other land uses – in fact, ITE guidelines state that their trip-generation rates data should not be used for land use projects in such locations. However, there is currently no method, tool, or data available in the U.S. to estimate trip-generation rates for such projects. This makes it extremely difficult to accurately estimate the transportation-related effects of such projects, or to implement appropriate multi-modal “mitigation measures” for people who may walk, bike, drive, or use public transit to travel to/from such sites.
Results: With ongoing input from a technical advisory Panel, UC Davis researchers collected trip-generation data at 30 smart growth land uses in California. They then used this information, along with trip-rates data from other studies, to develop a method embedded in a spreadsheet tool that can be used to adjust available trip-generation rates for “smart growth” land use projects proposed in California.
Products: This project produced a Final Overview Report with several technical Appendices; and a Tool to implement the Smart Growth Trip-Generation Adjustment Method:
- Final Overview Report
- Appendix A. Definition of “smart growth”
- Appendix B. Annotated review of land use & transportation literature
- Appendix C. Summary & Comparison of existing tools worldwide
- Appendix D. Evaluation of the operation & accuracy of available methodologies
- Appendix E. Data Collection Methodology and Results
- Appendix F. Methodology for Adjusting ITE Trip Generation Estimates for Smart Growth Projects
- WARNING:. This tool is only appropriate for sites in smart growth areas, as determined by the criteria on the first worksheet of the spreadsheet. The trip estimates produced by the tool are intended for planning-level analysis at single-use sites or for single land uses that are a part of ulti-use sites. The tool does not apply to multi-use developments as a whole. This is version 1.0 of the spreadsheet tool; updated versions may be posted at later dates. Please send comments and questions to Susan Handy at email@example.com.
In December 2013, the UC Davis team completed additional analysis using data collected by researchers at Portland State University, as described in: Verification and Re-estimation of the Smart Growth Trip Generation Model with Portland Data
For additional information about this project and its products, contact: Dr. Susan Handy, email: firstname.lastname@example.org.
Last updated 2/11/14