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

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Presentation on theme: "University of Minnesota Intersection Decision Support Research - Results of Crash Analysis University of Minnesota Intersection Decision Support Research."— Presentation transcript:

1 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

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

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

4 Potential Deployment 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%) Page 4 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 Potential Deployment Opportunities 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 Expressway* 18 Expressway* 8 2-Lane* 26 Source: Mn/DOT 2002 Crash Data Page 10 * NOTE: Number of Crashes Estimated

6 Potential Deployment Opportunities Selection Criteria: - State Highway System - Rural - Thru-Stop - 2000 to 2002 Crash Records 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 Page 11

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

8 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. 1 Crashes occurring in interchange areas and also at intersections, alleys and driveways. Source: Mn/DOT TH 52 Road Safety Audit Page 13 September 23, 2003 Severity Weighting: - Fatal = 5 - “A” Injury = 4 - “B” Injury = 3 - “C” Injury = 2 - PDO = 1

9 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. Page 14 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 Intersection Crash Type 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. 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) Page 15 September 23, 2003

11 Effect of Volume on 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. Source : Mn/DOT 2000 – 2002 Crash Data Page 16 September 23, 2003

12 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. Source: Mn/DOT 2000 – 2002 Crash Data Page 17 September 23, 2003 (A) (B)(C)

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

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

15 Page 7 Source: Traffic Safety Fundamentals Handbook

16 Page 8 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 Case Study: Change in Intersection Delay 749.5 2754.0 568.7 13631 0 2000 4000 6000 8000 10000 12000 14000 16000 Total Delay (Seconds) Major Street Delay Minor Street Delay Comparison of TOTAL PM Peak Hour Delay Source: Mn/DOT Peak Hour Turning Movements using Highway Capacity Software Through / STOP ControlTraffic Signal Control Page 9 Source: TH 244 / Wedgewood Drive Signal Analysis (Mahtomedi, MN); Howard R. Green Company

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

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

20 Candidate Intersections - At-Fault Driver Age Source: Mn/DOT 2000 – 2002 Crash Data Page 20 September 23, 2003 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.

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

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. Source: Mn/DOT 2000 – 2002 Crash Data Contributing Factors September 23, 2003 Right Angle Crash Location Page 22

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). Page 23

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... Page 24

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

26 US 52 & CSAH 9 NB SB Page 26 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.

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