About PAS Memo

Today's planners need to stay informed about innovative strategies and techniques for a wide range of planning topics.

PAS Memo delivers this information to you. It highlights current cutting-edge topics — such as green roofs and climate change adaptation — while providing the latest findings and best practices in classic planning areas such as stormwater management and housing affordability.

PAS Memo is written by practicing planners and experts in the field eager to share their expertise through illuminating case studies. Each article provides a list of links to online resources for planners who want to dig deeper.

PAS Memo is available to Planning Advisory Service subscribers only.

Current Issue

May/June 2013

Getting Trip Generation Right:
Eliminating the Bias Against Mixed Use Development

By Jerry Walters, Brian Bochner, and Reid Ewing

When planners, developers, or traffic engineers conduct traffic impact analyses for proposed developments, they typically use the trip-generation data and analysis methods published by the Institute of Transportation Engineers (ITE) in its Trip Generation report and Trip Generation Handbook. However, standard traffic engineering practice does not account for project characteristics such as the mix and balance of land uses, compactness of design, neighborhood connectivity and walkability, infill versus remote location, and the variety of transportation choices offered. This can have significant implications when the project in question is a mixed use development.

The conventional methods used by traffic engineers throughout the U.S. to evaluate traffic impacts fail to account for the benefits of mixed use and other forms of lower-impact development. They exaggerate estimates of impacts and result in excessive development costs, skewed public perceptions, and decision maker resistance. These techniques overlook the full potential for internalizing trips through interaction among on-site activities and the extent to which development with a variety of nearby complementary destinations and high-quality transit access will produce less traffic. These effects can reduce the number of vehicle trips generated to a far greater degree than recognized in standard traffic engineering practice.

Read the full article