The University of Utah
College of Architecture + Planning

Traffic Impacts of Mixed-Use Development

Current methods of traffic impact analysis, which rely on rates and adjustments from ITE, are believed to understate the traffic benefits of mixed-use developments (MXDs) and therefore to lead to higher exactions and development fees than necessary and to discourage otherwise desirable developments.

Building on our studies published in the journals of Transportation Research Record and Journal of Urban Planning and Development to improve the traffic impacts of MXDs which examined 13 regions, we are currently collecting data on 19 more metropolitan regions bringing our total data coverage to 32 regions. This project is unfunded. The research team for this project includes Dr. Guang Tian, PhD students Keunhyun Park and Sadegh Sabouri, and research assistants Alec Barton, Amanda Dillon and Brittany Harris.

“A mixed-use development or district consists of two or more land uses between which trips can be made using local streets, without having to use major streets. The uses may include residential, retail, office, and/or entertainment. There may be walk trips between the uses.”

In the previous study, standard protocols were used to identify and generate data sets for MXDs in 13 large and diverse metropolitan regions. Data from household travel surveys and geographic information system databases were pooled for these MXDs, and travel and built-environment variables were consistently defined across regions. Hierarchical modeling was used to estimate models for internal capture of trips within MXDs and for walking, biking, and transit use on external trips. MXDs with diverse activities on site were shown to capture a large share of trips internally, so that the traffic impacts of the MXDs were reduced relative to conventional suburban developments. Smaller MXDs in walkable areas with good transit access generated significant shares of walk, bike, and transit trips and thus also mitigated traffic impacts.

Findings from the first two studies are considerable:

  • 20% of trips stay within MXDs
  • 24% of trips consist of walk, bike, or transit modeshares

Read About Our Six-Region Study in Journal of Urban Planning and Development (September 2011)

Read About Our Thirteen Region Study in Transportation Research Record (2015)