The Challenges of Predicting Travel Behavior on Estimating Trip Generation: Local Traffic Impact Assessment in Four Southeastern and Mid-Atlantic States

(Original Title: Predicting Congestion: The Challenge of Shifting Travel Behavior on Estimating Trip Generation, Traffic and other System Impacts)

Research Team

Ruth Steiner, University of Florida
Noreen McDonald, University of North Carolina at Chapel Hill
Tabitha Combs, University of North Carolina at Chapel Hill

Project Description

In recent years, transportation professionals have become increasingly aware that transportation planning and engineering practices need to be matched to the context in which they occur and the population they serve. Communities, primarily urban ones, have struggled with how to measure traffic impacts of development in dense, mixed-use communities where residents can walk, bicycle, and use transit to get to destinations. Conventional traffic impact assessments are often based upon the Institute for Transportation Engineers (ITE) Trip Generation Handbook, which many argue is based upon auto-oriented suburban development. In 2017, ITE issued a position paper describing the purpose and need for a new recommended practice (RP) (Draft Update to Recommended Practice), which proposed a Multimodal Transportation Impact Assessment for Site Development, which would shift the emphasis from traffic (i.e., impact on highways) to transportation impact assessment. This project explores the implementation of traffic impact assessment (TIA) in urban communities throughout the Southeastern and Mid-Atlantic States. We conducted a literature and practice review of state and regional policies for transportation impact assessment to understand the framework within which local governments operate with respect to the preparation of TIA. Interviews with 93 cities and counties in four states – North Carolina, Virginia, Maryland, and Florida – were conducted to understand how cities and counties use innovative methods to conduct TIA. We learned that state regulations vary significantly across these states, and regional agencies have a limited role in traffic impact assessment. Local governments use a variety of innovations, including waivers and variances based on the characteristics of the development, requirements to accommodate non-auto modes, ad hoc modifications to project design, and adjusting the level of service measurements. This research can inform local governments about the options they have to modify transportation impact assessments to make them multimodal and context sensitive.

Product

Catalog of Traffic Impact Assessments (TIA) practices and innovations, categorized according to local characteristics and motivations for innovation – Developed a survey instrument that was administered to local governments. Based on the responses researchers developed a set of categories of innovative practices that local governments are using to conduct their TIAs (traffic impact assessments).