Improving Vehicle Trip Generation Estimations for Urban Contexts: A Method Using Household Travel Surveys to Adjust ITE Trip Generation Rates

The Institute of Transportation Engineers (ITE) Trip Generation Handbook has become the predominant method for estimating vehicle trips generated by development. The Handbook is often criticized for its inability to account for multimodal behavior in urban contexts, often over-estimating vehicle traffic. The purpose of this research is to develop and test a widely available, ready-to-use method for adjusting the ITE Handbook vehicle trip generation estimates for urban context using regional household travel survey data. Household travel surveys from Oregon, Washington and Maryland, as well as nationally available built environment data, were used. Three mode share/vehicle occupancy adjustment methods were estimated for nine general land use categories. One hundred and ninety five independently-collected establishment-level vehicle trip generation data were used to verify the performance of the methods compared with the Handbook. Six land use categories (out of the nine estimated) were able to be tested. ITE’s Handbook appeared to be more accurate for residential condominiums/townhouses, supermarkets and quality (sit-down) restaurants. Moderate or small improvements were observed for mid-rise apartments, high-turnover (sit-down) restaurants. The most substantial improvements occurred at high-rise apartments and condominiums/townhouses, shopping center, or coffee/donut or bread/donut/bagel shops without drive-through windows. For the adjustments tested analyzed, the simplest method provided comparable results to more complex adjustments. Additional data collections representing more land uses and time periods are necessary to determine how ITE’s Handbook performs in other circumstances, including assessing the transferability of the vehicle trip end rates or mode share reductions across regions.