A Comparative Analysis of Vehicle Trip Generation Methods at the 65th Street and Folsom Boulevard Smart Growth Development

Book excerpt: The purpose of this research project is to evaluate the accuracy of industry accepted vehicle trip generation methods for smart growth developments in the Sacramento Region. An existing smart growth development located at the intersection of 65th Street and Folsom Boulevard in Sacramento was chosen as the subject development. Estimates of generated vehicle trips for the daily, A.M. peak hour, and P.M. peak hour time periods were calculated using the Institute of Transportation Engineers (ITE) Multi-Use Trip Generation Method and the San Diego Association of Governments (SANDAG) Trip Generation for Smart Growth Method. The results were compared to observed vehicle trips at the subject development. The observed vehicle trips at the development were counted using automatic vehicle counters (pneumatic tubes) at each of the two driveways that provide ingress/egress to the development over a 24-hour period. The vehicle trip generation estimates were calculated using the direction provided by the Institute of Transportation Engineers and the San Diego Association of Governments. The inputs required to complete the calculations were obtained by contacting local government agencies and the owners and operators of the development. The required data included Geographical Information System (GIS) files to estimate employment and transit, which were provided by the Sacramento Area Council of Governments (SACOG) and Sacramento Regional Transit (RT). United States Census information was available online, and land use characteristics were provided by the owners and operators of the development. In the A.M. peak hour, the 516 vehicle trips estimated using the ITE Multi-Use Method was 108% of the 479 observed vehicle trips. The 322 vehicle trips the SANDAG Trip Generation for Smart Growth Method estimated in the A.M. peak hour was 67% of the 479 observed vehicle trips. In the P.M. peak hour, the 361 vehicle trips the ITE Multi-Use Method estimated was 42% of the 853 observed vehicle trips. The 472 vehicle trips estimated using the SANDAG Trip Generation for Smart Growth Method was 55% of the 853 observed vehicle trips. In the daily time period, the 6,250 vehicle trips the ITE Multi-Use Method estimated was 125% of the 4,976 observed vehicle trips. The 6,189 vehicle trips estimated using the SANDAG Trip Generation for Smart Growth Method was 124% of the 4,976 observed trips. The SANDAG Trip Generation for Smart Growth Method requires significantly more effort to produce vehicle trip generation results compared to the ITE Multi-Use Method. The SANDAG Trip Generation for Smart Growth Method requires research and analysis to identify the inputs its spreadsheet tool uses to calculate vehicle trip reductions for smart growth developments, which include using the U.S. Census, GIS software which is not readily available to all users to perform the analysis, and detailed and sophisticated analysis of travel analysis zones and regional transit travel times. The ITE Multi-Use Method is based on an initial calculation of vehicle trips and two easily obtained internal capture rate tables provided in the ITE Trip Generation Handbook.