Safety Study of I-35W Improvements Done Under UPA Project

Principal Investigator

Gary Davis, Professor, Civil, Environmental and Geo-Engineering


  • John Hourdos, Director, MN Traffic Observatory, Civil, Environmental and Geo-Engineering

Project Summary

Minnesota's Urban Partnership Agreement (UPA) project, completed in November 2010, consisted of a package of interventions aimed at improving travel on the I-35W corridor. Problem Statement NS-329 notes that there is interest in extending some or all of these interventions to other corridors and calls for an estimation of their safety effects to help make these decisions. Because the UPA intervention consisted of several different improvements—including reconstruction of the Crosstown Commons, provision of high-occupancy toll (HOT) lanes and priced dynamic shoulder lanes (PDSL), and changes in ramps/auxiliary lanes—NS-329 also states that it would be desirable to untangle the effects of the improvements. For example, crash frequencies appear to have increased where PDSL have been provided, but it is unclear if this is due to the PDSLs themselves or to changes in congestion resulting from removing the Crosstown bottleneck.

This project is using an interrupted time-series approach to test for changes in crash experience before versus after the UPA project(s). In addition to looking at an overall, aggregated effect, separate analyses are being conducted on important individual sections of the I-35W corridor for separate times of day to allow for congestion effects and separate crash types (rear-end, side-swipe, road departure).


  • Minnesota Department of Transportation

Project Details

  • Start date: 06/2014
  • Project Status: Completed
  • Research Area: Transportation Safety and Traffic Flow
  • Topics: None

Reports or Products: