Evaluation of Ranking Methods for Speed and Ice Crashes on the Oregon Highway Network

1. Evaluation of Ranking Methods for Speed and Ice Crashes on the Oregon Highway Network Peter G. Bosa Graduate Student, MURP Research Assistant, ITS

2. •••Excessive Speed • Over 20,000 crashes occurred on OR Highways in 2001 • (~50,000 in the entire state annually) • 27% of all crashes speed related • 36% of all fatal crashes speed related • Speed correlations to crashes: • Reduces driver’s ability to safely navigate around • curves or obstacles • Increases stopping distance • Increases driver reaction time Paraphrased from Bertini et al, 2004

3. •••Previous Work Results • Examination of the Impact of Speed upon Highway Safety: • An Oregon Perspective • (Robert Bertini, Casey Nolan, Carolyn Bonner, Tarek Abou El-seoud) • Examined 2001 Oregon Department of Transportation (ODOT) crash data • Identified ‘variables’ overrepresented in speed-related crashes

4. •••Goals of Current Project • Expand research to include 2000 to 2002 • Focus on ice as a contributing factor to • speed-related crashes • Develop a method by which to rank areas • by risk for speed and ice crashes

5. •••Initial Analysis 2000 - 2002

6. ODOT Highway Network Create one-mile highway segment file using mileposts Plot crash data using mileposts Update highway segments with crash data •••Creating Model

7. •••Results • 62,485 Total Crashes 2000-2002 on ODOT network • 16,865 Speed Crashes 2000-2002 (21% of Total) • 4,312 Speed & Ice Crashes 2000-2002 (7% of Total)

8. •••Results • Max # of crashes: 596 on US 99E • (MLK Ave between Burnside and Powell) • Mean: 11 • Median: 3

9. •••Results • High frequencies located near urban areas

10. •••Results • Highest percentages along rural highways

11. •••Ranking Methods ••Frequency

12. •••Ranking Methods ••Rate (Crashes ÷ MVMT)

13. •••Ranking Methods Critical Ranking Method RC = critical rate RA = the average rate for similar facility K = probability constant based on desired level of significance (1.645 for 95%) M = millions of VMT or entering vehicles = (V*D*L)/1,000,000

14. •••Ranking Methods ••Statewide RQC

15. •••Ranking Methods ••Zonal RQC

16. •••Ranking Methods ••Zonal RQC

17. •••Ranking Methods ••Comparison

18. •••Ranking Methods ••Comparison

19. •••Ranking Methods ••Comparison Wilcoxon Rank Sum Test

20. •••Profiles

21. •••Conclusions • Icy road conditions contribute to speed- • related crashes • Most pronounced in rural, mountainous • terrain where environmental and roadway • characteristics amplify risks • Rate Quality Control Methods useful in • determining those segments of roadway • most at risk

22. •••Next Steps • Survey and inventory of top ranking sites • (curves, shoulder width, grade, wind…) • Research will assist in identification of • sites best suited for deployment of • ‘dynamic speed-warning signs’

23. •••Acknowledgements • Dr. Chris Monsere & Dr. Robert Bertini, PSU • Delia Chi & Sirisha Kothuri, PSU • Oregon Department of Transportation