1. Characterizing Interstate Crash Rates Based on Traffic Congestion Using Probe Vehicle Data Michelle M. Mekker, Stephen M. Remias, Margaret L. McNamara, Darcy M. Bullock

2. Outline Introduction and Motivation Data Sources Fatal Interstate Crashes, 2012-2014 All Interstate Crashes, 2014 Conclusion

3. Congestion impacts both safety and mobility Common causes of congestion Daily commute (recurring) Crash Construction Weather Two types of congestion-related crashes Within-queue: low speed, low severity Back-of-queue: high speed differential, high severity 8/15/2013 – 7 Fatalities 7/31/2013 – 1 Fatality 2/2/2015 – 1 Injury Introduction and Motivation

4. Outline Introduction and Motivation Data Sources Fatal Interstate Crashes, 2012-2014 All Interstate Crashes, 2014 Conclusion

5. Data Sources Crowd Sourced Probe Vehicle Data Data Point 5

6. Data Sources Crowd Sourced Probe Vehicle Data TMC Segments End of Queue within 5 miles INRIX XD Segments End of Queue within 2 miles

7. Data Sources Crowd Sourced Probe Vehicle Data – Tools

8. Data Sources Crowd Sourced Probe Vehicle Data – Tools

9. Requirements for use of data in study: 1/1/2012-12/31/2014 Travel lane crashes only Known, reliable location Accurate time of crash Occurred on Indiana Interstates Data Sources Crash Database

10. 1.7-hour queue duration before secondary crash occurred Data Sources Example of Secondary Crash with Probe Vehicle Data

11. INRIX Trip Trace Graph from Crash on I-65 on 2/2/2015 12:0011:3011:0010:3010:0009:3009:0008:3008:0007:30 215 220 200 230 225 210 205 Mile Markers Local Time <=10 mph 10 - 20 mph 20 - 40 mph 40 - 60 mph >60 mph > 1.5 Hours i iii ii iv Data Sources Example of Secondary Crash with Probe Vehicle Data i)Initial queue forms (8:34) ii)Crash occurs (10:16) iii)Maximum queue length (11:34) iv)Queue clears (12:14)

12. Class Duration (minutes) Speed (mph) ω1ω1 Backward Forming 87 1.03 ω2ω2 Frontal Stationary 95 -- ω3ω3 Backward Recovery 10 12 ω4ω4 Backward Forming 115 3.78 ω5ω5 Frontal Stationary 40 -- ω6ω6 Backward Recovery 50+ 7.2 ω7ω7 Rear Stationary 15+ -- Shockwave Diagram from Crash on I-65 on 2/2/2015 Data Sources Example of Secondary Crash with Probe Vehicle Data

13. Outline Introduction and Motivation Data Sources Fatal Interstate Crashes, 2012-2014 All Interstate Crashes, 2014 Conclusion

14. 77 82 71 30 out of 230 fatal crashes occurred at the back of a queue Fatal Interstate Crashes, 2012-2014 87% of fatal back- of-queue crashes involved trucks 39% of fatal non-back- of-queue crashes involved trucks

15. T T T T T T T T T T T T T T T T T T T T T T T TTTT T Truck/s Involved Fatal Interstate Crashes, 2012-2014 Queue Duration 63% of fatal back-of- queue crashes had a queue duration of > 60 minutes

16. Outline Introduction and Motivation Data Sources Fatal Interstate Crashes, 2012-2014 All Interstate Crashes, 2014 Conclusion

17. All Interstate Crashes, 2014 Queue Duration

18. n = 3448 (22.8%) All Interstate Crashes, 2014 Queue Duration 75% of congestion crashes had a queue duration of ≥ 14 minutes 50% of congestion crashes had a queue duration of ≥ 41 minutes 25% of congestion crashes had a queue duration of ≥ 120 minutes

19. All Interstate Crashes, 2014 More vehicles = More opportunities for a crash to occur Crash Rate = Average Crash Frequency in a Period Exposure in Same Period What is the difference in crash rate? Congested Uncongested

20. Congested Uncongested All Interstate Crashes, 2014 Mile-Hours as Exposure Uncongested Crash Rate = Number of crashes in uncongested traffic conditions Segment length x Number of uncongested hours Congested Crash Rate = Number of crashes in Congested traffic conditions Segment length x Number of Congested hours

21. All Interstate Crashes, 2014 Mile-Hours as Exposure Most of operation is uncongested

22. 0.4 2.1 0.5 0.2 1.3 0.7 1.1 0.7 2.0 1.0 4.6 1.2 Thousands of Congested Mile-Hours in 2014 All Interstate Crashes, 2014 Mile-Hours as Exposure

23. Overall Ratio = 24.1 All Interstate Crashes, 2014 Congested vs. Uncongested Crash Rates Crash Rate Ratio = Congested Crash Rate Uncongested Crash Rate

24. Rural Interstate Segments as Defined by Metropolitan Statistical Areas (census-based) All Interstate Crashes, 2014 Rural vs. Urban

25. Rural Crashes Overall Rural Ratio = 23.8 Overall Urban Ratio = 20.7 Urban Crashes All Interstate Crashes, 2014 Rural vs. Urban

26. Outline Introduction and Motivation Data Sources Fatal Interstate Crashes, 2012-2014 All Interstate Crashes, 2014 Conclusions

27. Only 1-2% of interstate operation was congested Of fatal crashes over 3 years 13% were back-of-queue crashes 63% of back-of-queue fatal crashes had queue durations > 60 minutes 87% of back-of-queue fatal crashes involved commercial vehicles Of all crashes in 2014 22.8% were congestion-related crashes 75% had queue duration > 14 minutes Crash rate is 24.1 times greater when congestion/queue is present Overall Ratio = 24.1 Conclusions