Evaluating The Relevancy Of Current Crash Test Guidelines For Roadside Safety Barriers On High Speed Roads

Transcription

1 Evaluating The Relevancy Of Current Crash Test Guidelines For Roadside Safety Barriers On High Speed Roads Connie Xavier Dominique Lord Chiara Dobrovolny Roger Bligh TRB 1 st International Roadside Safety Conference June 12-15, 2017

2 Acknowledgements Texas Department of Transportation Marcie Perez, TTI Undergraduate Research Scholars Program Mike Pratt, TTI Texas A&M GIS Department

3 Introduction Higher speed limits across the United States

4 Introduction MASH testing criteria Test Level 3: passenger vehicles impacting at 25 and 62 mph (High speed roads) Impact speed is 85th percentile impact speed of real-world crashes

5 Introduction Past research showed that the impact angle does not vary greatly with functional class Computer simulations and full-scale crash tests have found stability concerns with higher speed impacts

6 Do high speed roads influence the severity of injuries? Does injury severity factor significantly increase as posted speed limit increases for real world accidents against barriers? If yes, further study to determine impact conditions on highways over 75 mph could be warranted.

7 Study Objective 75 mph 80 mph 70 mph Compare Injury Severity 85 mph

8 Approach Step 1 Obtain Crash Data Step 2 Step 3 Summary of Data Crash Severity Analysis Plots of Crashes Statistical Significance

9 Limitations Information on actual impact speed not provided in crash databases (need crash reconstruction and police reports) No investigation on impact orientation Mostly observation between impact severity and posted speed limit Is high injury severity due to barrier failure to safely redirect vehicle? Is high injury severity related to higher impact speed during crash? Is 62 mph testing speed appropriate for hardware design for very high speeds?

10 1. Obtain Crash Data TxDOT s CRIS crash database Data was filtered: single-vehicle single-occupant run-off-road crashes posted speed limit of and greater than 70 mph first harmful event being a roadside safety barrier Concrete traffic barrier, guardrail, median barrier, retaining wall, bridge rail

11 2. Summary of Data Number of Barrier Crashes by Speed Limit and Year Total No Speed Limit Data mph mph mph mph Total

12 2. Summary of Data Number of Barrier Crashes by Speed Limit and Year Total No Speed Limit Data mph mph mph mph Total

13 2. Summary of Data Number of Barrier Crashes for Each Roadway System Total Alternate Business Interstate Business US County Road Farm to Market Interstate Local Road/Street Ranch Road Spur State Highway State Loop Toll Road US Highway Total

14 2. Summary of Data Number of Barrier Crashes for Each Roadway System Total Alternate Business Interstate Business US County Road Farm to Market Interstate Local Road/Street Ranch Road Spur State Highway State Loop Toll Road US Highway Total

15 2. Summary of Data Conclusions: 1. 3 Speed Limit Categories 70 mph 75 mph 80 mph 2. Crashes on State Highways and Interstates

16 3. Crash Severity Analysis Injury Severity Color Scale Color Injury Severity Fatal Incapacitating Injury Non-Incapacitating Injury Possible Injury Property Damage Only K A B C O

17 mph mph K A B C O mph mph

18 mph mph K A B C O mph mph

19 mph mph K A B C O mph mph

20 % of total crashes Results of Crash Severity Analysis % of total crashes mph 75 mph 80 mph mph 75 mph 80 mph % of total crashes % of total crashes K + A B C O mph 75 mph 80 mph mph 75 mph 80 mph

21 Crash Severity Percentages K+A percentage category consistently increases from 70 mph to 80 mph posted speed limit roads for all years Years that did report a K+A injury severity on 75 mph roads showed an increase in K+A severity as the posted speed limit increased There was a decrease in the percentage of PDO crashes on 70 mph roads to 80 mph roads for years , suggesting that more crashes resulted in more severe injuries

22 Results of Crash Severity Analysis Combined Data for Years % of total crashes mph 75 mph 80 mph K+A B C O

23 Conclusions Plots of crashes showed that the fatal and incapacitating injuries are not concentrated in one particular area, but some highways experienced more severe injuries consistently for consecutive years The K+A percentages between the 70 mph and 80 mph were not statistically different at the 5% significance level for every year Can be attributed to the small sample size issue The K+A percentages for the combined data showed significance at the 5% level between 70 mph and 80 mph posted speed limit roads Shows possibility that the severity of injuries increases as the posted speed limit increases

24 Future Work Look at police reports Individually define injuries Look at the manner the vehicle hit the barrier Reconstruction of crashes to find impact speed Look at data for more years once they become available Develop a baseline to compare the trend in injury severities of lower speed ranges (less than 70 mph) to higher speed ranges Look at severity of injury by roadside barrier type in greater details

25 Questions?