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University of Minnesota Intersection Decision Support Research - Results of Crash Analysis

University of Minnesota Intersection Decision Support Research - Results of Crash Analysis. Presented at IDS Quarterly Review January 15, 2004. Page 2. Agenda. Deployment Opportunities Rural Roadway Safety Issues Rural Intersection Safety Issues

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University of Minnesota Intersection Decision Support Research - Results of Crash Analysis

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  1. University of Minnesota Intersection Decision Support Research - Results of Crash Analysis Presented at IDS Quarterly Review January 15, 2004

  2. Page 2 Agenda • Deployment Opportunities • Rural Roadway Safety Issues • Rural Intersection Safety Issues • Candidate Intersections for the IDS Research Modeling • Conclusions

  3. Page 3 Concept of “Critical Crash Rate” Source: Traffic Safety Fundamentals Handbook

  4. Page 4 PotentialDeployment Opportunities • Initial Thoughts About Deployment • Highest Priority: 2-Lane & Expressway thru-STOP intersections with crash rate greater than critical crash rate. • How Many Intersections in the State Highway System? Total>CR (% of total) • 2-Lane - 3,388 | 104 (~ 3%) • Expressway - 396 | 23 (~ 6%) Statewide Crashes: - Statewide: 117,151 - Rural: 46,998 - Expressway: 10,996 - Intersection: 4,231 - Fatal: 70 - “A” Injury: 143 - 2-Lane: 23,179 - Intersection: 6,838 - Fatal: 121 - “A” Injury: 237

  5. Page 10 PotentialDeployment Opportunities * NOTE: Number of Crashes Estimated Statewide Fatal Crashes 590 State Highway System - 287 fatal crashes - 11,900 miles of road - 33 Billion VMT County and Local Roads - 303 fatal crashes - 123,400 miles of road - 22 Billion VMT Urban 83 Rural 204 Urban 82 Rural 221 Segment & Other TCD* ~ 150 Thru-STOP* ~ 45 Signalized* ~ 9 Segment & Other TCD* ~ 162 Thru-STOP* ~ 49 Signalized* ~ 10 2-Lane* 26 Expressway* 18 Expressway* 8 Source: Mn/DOT 2002 Crash Data

  6. Page 11 PotentialDeployment Opportunities Intersections with 2 Fatal Crashes 7 Expressway 5 Two-Lane 2 Crash Rate > Critical 4 Crash Rate > Critical 2 Crash Rate < Critical 1 Crash Rate < Critical 0 Selection Criteria: - State Highway System - Rural - Thru-Stop - 2000 to 2002 Crash Records

  7. Page 12 Differences in Roadway Type 8,887 mi. 56 mi. 94 mi. 840 mi. 817 mi. September 23, 2003 Source: Mn/DOT 2000-2002 Crash Data

  8. Page 13 Effect of Volume on Rural Expressway Crash Rates • NOTE: • Both crash rate and severity rate are seen to increase as the volume increases. • Unlike the crash and severity rate, the fatality rate decreases as the roadway volume increases. • Similar to the crash rate and severity rate, the percent of intersection related crashes increases with volumes. • 1Crashes occurring in interchange areas and also at intersections, alleys and driveways. September 23, 2003 Severity Weighting: - Fatal = 5 - “A” Injury = 4 - “B” Injury = 3 - “C” Injury = 2 - PDO = 1 Source: Mn/DOT TH 52 Road Safety Audit

  9. Page 14 Intersection Crash& Severity Rates • NOTE: • Rural expressway thru-STOP intersections have similar crash and severity rates to all rural thru-STOP intersections. • The average crash rate of intersections over the critical crash rate is twice the crash rate of all rural thru-STOP intersections. • The average severity rate of intersections over the critical crash rate is three times the severity rate for all rural thru-STOP intersections. • US 52 intersections over the critical crash rate have a nearly identical crash rate and severity rate when compared to rural expressway intersections over the critical crash rate. September 23, 2003 Source: Rural Thru-STOP: Mn/DOT 2000 – 2002 Crash Data Rural Expressway Thru-STOP: Mn/DOT 2000 – 2002 Crash Data Rural Expressway Thru-STOP – Over Critical Crash Rate: Mn/DOT 2000 – 2002 Crash Data US 52: US 52 Road Safety Audit (January 1999 – March 2002 Crash Data)

  10. Page 15 Intersection CrashType Distribution • NOTE: • Thru-STOP intersections for rural expressways have a higher percentage of right angle crashes in comparison to all rural thru-STOP intersections. Most other crash types show a decrease. • The percentage of right angle crashes significantly increases for rural expressway intersections over the critical crash rates. • US 52 intersections over the critical crash rate are nearly identical to the crash type distribution of all rural expressway intersections over the critical crash rate. September 23, 2003 Source: Rural Thru-STOP: Mn/DOT 2000 – 2002 Crash Data Rural Expressway Thru-STOP: Mn/DOT 2000 – 2002 Crash Data Rural Expressway Thru-STOP – Over Critical Crash Rate: Mn/DOT 2000 – 2002 Crash Data US 52: US 52 Road Safety Audit (January 1999 – March 2002 Crash Data)

  11. Page 16 Effect of Volumeon Right Angle Crashes • NOTE: • The “Medium” and “Large” volume increments strongly show that the average number of right angle crashes increases as volumes increase. • The “Small” volume increments tend to support that right angle crashes increase with volume, but the small number of intersections in each volume category results in more fluctuations. September 23, 2003 Source: Mn/DOT 2000 – 2002 Crash Data September 23, 2003

  12. Page 17 Severity of Right Angle Crashes • NOTE: • The percent of right angle crashes at rural, thru-STOP intersections that result in a fatality is approximately twice that for all rural, thru-STOP intersection crashes. • Right angle crashes are also more likely to result in an injury crash. (A) (B) (C) September 23, 2003 Source: Mn/DOT 2000 – 2002 Crash Data

  13. Page 5 Will Signal WarrantsBe Met on Expressways? Of the 23 Rural Expressway Intersections Over the Critical Crash Rate: - 2 expected to meet Warrant 1A and 4 expected to meet Warrant 1B. - If the 30% volume reduction used, then 6 expected to meet Warrant 1A and 9 expected to meet Warrant 1B.

  14. Page 6 Will Signal WarrantsBe Met on 2-Lane Roads? Of the 104 Rural 2-Lane Intersections Over the Critical Crash Rate: - 1 expected to meet Warrant 1A and 2 expected to meet Warrant 1B. - If the 30% volume reduction used, then 6 expected to meet Warrant 1A and 5 expected to meet Warrant 1B.

  15. Page 7 Source: Traffic Safety Fundamentals Handbook

  16. Page 8 DEPARTMENT OF TRANSPORTATION MINNESOTA • HIGHLIGHTS: • Traditionally the installation of a traffic signal was expected to result in an increase in total and rear end crashes and a decrease in right angle crashes and severity. • Before vs. After studies of traffic signal installations along TH 52 and TH 14 generally indicate similar trends: • Total crashes, PDO crashes and rear end crashes increased. • Right angle and fatal crashes were reduced. • The number of injury crashes remained about the same. • The project in Byron also illustrated the crash rate regressing to the mean for similar signalized intersections. Typical Results of Traffic Signal Installation

  17. Page 9 16000 14000 12000 Major Street Delay Minor Street Delay 10000 8000 Total Delay (Seconds) 13631 6000 4000 568.7 2000 2754.0 749.5 0 Through / STOP Control Traffic Signal Control Source: Mn/DOT Peak Hour Turning Movements Comparison of TOTAL PM Peak Hour Delay using Highway Capacity Software Case Study:Change in Intersection Delay Source: TH 244 / Wedgewood Drive Signal Analysis (Mahtomedi, MN); Howard R. Green Company

  18. Page 18 Rural Expressway IntersectionsOver the Critical Rate • Evaluating Criteria: • High Crash Rate • High Frequency • of Crashes • High Percentage • of RA Crashes September 23, 2003 1Intersection is being replaced with an interchange as part of US 52 Design-Build. 2An overpass is programmed for construction in FY 2004. 3Intersection located in influence area for a new signal installed at CSAH 46.

  19. Page 19 Candidate Intersections - Summary Table September 23, 2003

  20. Page 20 Candidate Intersections - At-Fault Driver Age • NOTE: • Young” drivers are over represented in crashes at the intersection of US 10 & CR 43. • “Old” drivers are over represented in crashes at the intersection of US 52 & CSAH 9. September 23, 2003 Source: Mn/DOT 2000 – 2002 Crash Data

  21. Page 21 Candidate Intersections - Crash Type Distribution September 23, 2003 Source: Mn/DOT 2000 – 2002 Crash Data

  22. Page 22 Candidate Intersections -Right Angle Crashes • NOTE: • Nearly 80% of right angle crashes at the candidate intersections occurred on the farside of the intersection (i.e., when vehicle on minor street is pulling out of median cross-over). • At the candidate intersections, nearly 90% of all right angle crashes were “Stopped, Pulled Out” while no “Ran the STOP” crashes were observed. Right Angle Crash Location Contributing Factors September 23, 2003 Source: Mn/DOT 2000 – 2002 Crash Data September 23, 2003

  23. Page 23 Conclusions • There are safety issues along segments of rural roadway - crash frequencies appear to increase significantly as volume increase. • There are safety issues at rural Thru-STOP intersections - the severity and frequency of right angle crashes are a particular concern • Intersections with unusually high crash frequencies (greater than the critical Rate) are different than “normal” intersections - not only are there more crashes but the distribution is also different (more right angle crashes).

  24. Page 24 Conclusions cont’d • The primary contributing factor to right angle crashes at rural thru-STOP intersections is gap selection and this becomes more critical at higher traffic volumes (because there are fewer safe gaps to select). • The best candidate intersection to include in the IDS research is...

  25. Page 25 Recommended Candidate for Operational Test - US 52 & CSAH 9 CSAH 9 U.S. 52

  26. Page 26 US 52 & CSAH 9 • Intersections has a high percentage of right angle crashes (65%). • 33% of at-fault drivers in crossing path crashes are over the age of 64. • US 52 corridor from Inver Grove Heights to Rochester has nearly one-quarter of rural expressway, thru-STOP intersections over the critical crash rate. NB SB

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