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
Acknowledgements Texas Department of Transportation Marcie Perez, TTI Undergraduate Research Scholars Program Mike Pratt, TTI Texas A&M GIS Department
Introduction Higher speed limits across the United States
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
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
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.
Study Objective 75 mph 80 mph 70 mph Compare Injury Severity 85 mph
Approach Step 1 Obtain Crash Data Step 2 Step 3 Summary of Data Crash Severity Analysis Plots of Crashes Statistical Significance
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?
1. Obtain Crash Data TxDOT s CRIS crash database Data was filtered: 2010-2013 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
2. Summary of Data Number of Barrier Crashes by Speed Limit and Year. 2010 2011 2012 2013 Total No Speed Limit Data 4 5 63 288 360 70 mph 1601 1696 1795 1442 6534 75 mph 7 27 910 2012 2956 80 mph 14 23 51 106 194 85 mph - - - 14 14 Total 1626 1751 2819 3862 10058
2. Summary of Data Number of Barrier Crashes by Speed Limit and Year. 2010 2011 2012 2013 Total No Speed Limit Data 4 5 63 288 360 70 mph 1601 1696 1795 1442 6534 75 mph 7 27 910 2012 2956 80 mph 14 23 51 106 194 85 mph - - - 14 14 Total 1626 1751 2819 3862 10058
2. Summary of Data Number of Barrier Crashes for Each Roadway System. 2010 2011 2012 2013 Total 70 75 80 70 75 80 70 75 80 70 75 80 Alternate 1 - - 1 - - - - - 6 - - 8 Business Interstate 3 - - 1 - - 3 - - 1 - - 8 Business US - - - - - - 1 - - 4 - - 5 County Road - - - - - - 1 - - - - - 1 Farm to Market 55 - - 52 - - 71 1-81 6-266 Interstate 739 4 14 780 14 23 560 814 38 355 1359 89 4789 Local Road/Street 6 - - 9 - - 7 2-14 4-42 Ranch Road 1 - - 1 - - - 26-1 - - 29 Spur 1 - - 2 - - - - - - 2-5 State Highway 179 - - 194 3-321 - 7 216 214 13 1147 State Loop 38 - - 37 1-54 2-82 11-225 Toll Road 286 - - 296 5-292 9 6 336 29 18 1276 US Highway 292 3-323 4-485 56-346 387-1896 Total 1601 7 14 1696 27 23 1795 910 51 1442 2012 120 9698
2. Summary of Data Number of Barrier Crashes for Each Roadway System. 2010 2011 2012 2013 Total 70 75 80 70 75 80 70 75 80 70 75 80 Alternate 1 - - 1 - - - - - 6 - - 8 Business Interstate 3 - - 1 - - 3 - - 1 - - 8 Business US - - - - - - 1 - - 4 - - 5 County Road - - - - - - 1 - - - - - 1 Farm to Market 55 - - 52 - - 71 1-81 6-266 Interstate 739 4 14 780 14 23 560 814 38 355 1359 89 4789 Local Road/Street 6 - - 9 - - 7 2-14 4-42 Ranch Road 1 - - 1 - - - 26-1 - - 29 Spur 1 - - 2 - - - - - - 2-5 State Highway 179 - - 194 3-321 - 7 216 214 13 1147 State Loop 38 - - 37 1-54 2-82 11-225 Toll Road 286 - - 296 5-292 9 6 336 29 18 1276 US Highway 292 3-323 4-485 56-346 387-1896 Total 1601 7 14 1696 27 23 1795 910 51 1442 2012 120 9698
2. Summary of Data Conclusions: 1. 3 Speed Limit Categories 70 mph 75 mph 80 mph 2. Crashes on State Highways and Interstates
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
2010 70 mph 2011 70 mph K A B C O 2012 70 mph 2013 70 mph
2010 75 mph 2011 75 mph K A B C O 2012 75 mph 2013 75 mph
2010 80 mph 2011 80 mph K A B C O 2012 80 mph 2013 80 mph
% of total crashes Results of Crash Severity Analysis % of total crashes 100 80 60 40 20 0 100 80 60 40 20 0 2010 15.38 2.99 70 mph 75 mph 80 mph 2012 11.11 2.58 2.91 70 mph 75 mph 80 mph % of total crashes % of total crashes K + A B C O 100 80 60 40 20 0 100 80 60 40 20 0 2011 4.18 8.7 70 mph 75 mph 80 mph 2013 3.9 4.04 6.93 70 mph 75 mph 80 mph
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 2010-2012, suggesting that more crashes resulted in more severe injuries
Results of Crash Severity Analysis Combined Data for Years 2010-2013 % of total crashes 90 80 70 60 50 40 30 20 10 0 2010-2013 3.38 3.61 8.79 70 mph 75 mph 80 mph K+A B C O
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 2010-2013 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
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
Questions?