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3.0 DATA ANALYSIS

The safety data test plan will focus on comparing pre-deployment crash and incident data with post-deployment crash and incident data. The data will be used to assess the measures of effectiveness outlined in the safety analysis and to estimate the safety cost savings from the UPA projects for the cost benefit analysis.

Members of the Battelle team will conduct a visual inspection of the data and will use automated range checks to identify any outliers or suspect data. Any data concerns identified will be checked with Mn/DOT and other agency personnel and the appropriate action will be taken.

Examples of the measures and analysis to be used in examining the safety data are highlighted below. Appropriate statistical measures, such as testing for significance, will be applied.

  • Total numbers of crashes. The total number of crashes on different highways and roadways will be compared pre- and post-deployment. To the extent data are available, total crashes on I-35W South, I-35W North, Cedar Avenue, Highway 77, County Road 23, Marquette, and Second Avenues in downtown Minneapolis will be documented and compared. The total number of crashes in the control corridors and region-wide trends will also be monitored.
  • Spatial configuration of crashes. The location or spatial configuration of crashes on the various facilities will also be analyzed pre- and post-deployment. This analysis will assist in determining if the UPA projects have reduced crashes in certain locations or have increased crashes in certain locations.
  • Types and severity of crashes. The types and the severity of crashes will be examined pre- and post-deployment based on available data. This analysis will assess potential changes in the nature of crashes, and the resulting severity, based on the UPA projects.
  • Crashes per 1,000 VMT. This analysis will compare pre- and post-deployment crashes per 1,000 VMT, based on available data from the traffic data test plan. This measure normalizes crash rates to account for either increased or decreases in VMT. Data will be examined for I-35W, Highway 77, the control corridors, the overall metropolitan area, and other facilities.
  • Incident response time. The response time to incidents on I-35W will be examined pre- and post-deployment of the UPA projects.
  • Incident duration time. The duration of incidents on I-35W will be compared pre- and post-deployment of the UPA projects.