1. Rural Intersection Decision Support - Crash Analysis Rural Intersection Decision Support - Crash Analysis Presented at Pooled Fund Meeting April 19, 2004

2. Overview The Goals Process for Individual States Crash Analysis What We Need Page 2

3. The Goals Statewide Review of Rural Thru-STOP Intersections to Identify Patterns. –Two-Lane –Expressway –Other? Identify Candidate Intersections for Field Deployment. –Focus on locations with a documented safety deficiency and crashes susceptible to correction by installation of the Driver Infrastructure Interface (DII). –Detailed review of up to 5 intersections.

4. Process for Individual States Visit State DOT –Collect available crash information. –Learn about the crash record system’s characteristics. –Discuss where analysis should be focused (i.e., two-lane or expressway or both). Crash Analysis –Identify pool of potential candidate intersections. –Screen/prioritize candidate intersections using Critical Crash Rate, crash severity and frequency of crashes susceptible to correction (i.e., straight crossing path). –Identify Top 5 Intersections for field deployment.

5. Process for Individual States State Review –Review, adjust, and/or approve Top 5 candidate intersections. More Crash Analysis –Detailed review of final Top 5 candidates. Visit State DOT –Present findings from the Statewide review and for the Top 5 candidate intersections. –State selects intersection for field deployment.

6. Crash Analysis - The Minnesota Process All Rural Thru-STOP Intersections 4-Legged; Expressways 4-Legged; Two-Lane Roadways Separate by facility type. Candidate Intersections, Expressways Identify intersections over the critical crash rate. Top 5 Candidates Identify intersections with high crash frequency, severity, and number of crossing path crashes. State DOT Selection of Test Intersection Detailed review of crash conditions. Advantages of the MN Process: - Research team familiar with this process, - Provides for statistical reliability, and - Identified MN intersection which agencies agreed upon. Candidate Intersections, Two-Lane

7. Crash Analysis - Statewide Review 3,784 Intersections Crash Rate = 0.4 Severity Rate = 0.6 198 Intersections Crash Rate = 0.4 Severity Rate = 0.7 1,174 Intersections Crash Rate = 0.5 Severity Rate = 0.9 All Rural Thru-STOP Intersections 4-Legged; Expressways 4-Legged; Two-Lane Roadways Separate by facility type. Candidate Intersections, Expressways Top 5 Candidates State DOT Selection of Test Intersection Candidate Intersections, Two-Lane

8. Crash Analysis - Statewide Review Begin with all rural thru-STOP intersections. –Need to be able to identify intersection by: Location - Rural vs. Urban Intersection Control - Thru-STOP Facility Type through roadway - Two-Lane vs. Expressway –Intersections with 4 approaches are preferred. For each group of intersections, determine the “expected” –Crash rate, –Severity rate, and –Crash type distribution. Crash Severity Factors: Fatal = ? (MN = 5) “A” Inj. = ? (MN = 4) “B” Inj. = ? (MN = 3) “C” Inj. = ? (MN = 2) PDO = ? (MN = 1)

9. Crash Analysis - Identify Candidate Intersections 23 Intersections Crash Rate = 0.9 Severity Rate = 1.8 All Rural Thru-STOP Intersections 4-Legged; Expressways 4-Legged; Two-Lane Roadways Candidate Intersections, Expressways Identify intersections over the critical crash rate. Top 5 Candidates State DOT Selection of Test Intersection Candidate Intersections, Two-Lane 104 Intersections Crash Rate = 1.6 Severity Rate = 2.9

10. Crash Analysis - Identify Candidate Intersections Use Critical Crash Rate to Identify Candidate Intersections –Statistically accounts for random nature of crashes. +

11. Crash Analysis - Identify Top 5 Candidates All Rural Thru-STOP Intersections 4-Legged; Expressways 4-Legged; Two-Lane Roadways Candidate Intersections, Expressways Top 5 Candidates Identify intersections with high crash frequency, severity, and number of crossing path crashes. State DOT Selection of Test Intersection Candidate Intersections, Two-Lane

12. Crash Analysis - Identify Top 5 Candidates Screen Candidate Intersections for Top 5 Candidates Based on: –High crash frequency, –High crash severity, Fatal and Serious Injury crashes –High number of crashes susceptible to correction by installation of the DII. Right angle…see following slide

13. Correctable Crash Types GES Crossing Path Crash Designations

14. Crash Analysis - State DOT Selection of Test Intersection All Rural Thru-STOP Intersections 4-Legged; Expressways 4-Legged; Two-Lane Roadways Candidate Intersections, Expressways Top 5 Candidates State DOT Selection of Test Intersection Detailed review of crash conditions. Candidate Intersections, Two-Lane

15. Crash Analysis - State DOT Selection of Test Intersection Review crash records for factors that may identify best candidate. –At-Fault driver’s age –Severity of correctable crashes –Crash type distribution –Weather and visibility conditions –Contributing factors Ran-the-STOP Stopped, Pulled Out –Crash location for divided roadways Farside Nearside NOTE: May need access to Police Officer reports to determine the at-fault driver and identify the contributing factors.

16. What We Need... For the Statewide Crash Analysis –Expected crash rate and severity rate for “similar” intersections OR crash summary for all rural thru-STOP intersections (see next slide). –Intersection approach volumes. –Crash records for rural thru-STOP intersections from the past 3 years. –Crash record information should include at least the Crash Type/Diagram and Crash Severity.

17. Example Mn/DOT Crash File Statewide Intersection Summary Intersection Attributes: - Rural vs. Urban - Traffic Control Device - Roadway type Information can be used to determine expected rates for a group of intersections and if individual intersections are above the critical crash rate (i.e., candidate intersections).

18. Example Mn/DOT Crash File Intersection Crash Report Imported into Excel Information can be used to identify Top 5 Candidates.

19. What We Need... For the Analysis of Top 5 Candidates –Crash record information also needs to include At-Fault driver’s information, Roadway surface conditions, Weather and visibility conditions, Contributing factors, and Crash location. –May need police officer reports from the past 3 years.

20. Example Mn/DOT Crash File Intersection Crash Report Information can be used to screen the Top 5 Candidates. Light - 1 = Daylight 2 = Sunrise Etc. Weather - 1 = Clear 2 = Cloudy 3 = Rain Etc. Action - 1 = Straight 6 = Left Turn Etc. Factor - 2 = Failure to Yield 3 = Speed 15 =Inattention Etc.

21. In Conclusion Following this process in Minnesota resulted in the identification of a large pool of candidate intersections. The prioritization process screened the intersections down to a Top 3 short list. The supplemental analysis provided the information that supported Mn/DOT’s selection of an intersection for the Field Operations Test. –US 52 and Goodhue County 9. Next Steps –Meetings with Individual State DOT Technical Liaisons. –Obtaining individual State’s crash records. –Analysis of the data.

22. Questions