Abstract:
Current crash test guidelines are contained in the Manual for Assessing Safety Hardware (MASH), which defines 62 mph being the 85th percentile impact speed for high speed roads. A crash data analysis of high speed roads in Texas with posted speed limits of 70, 75, 80, and 85 mph was performed to investigate whether MASH’s current test guidelines are applicable for roadside safety appurtenances placed on roads with posted speed limits greater than 75 mph. A representative sample of real-world, single-vehicle, run-off-road crashes involving longitudinal barriers as the first harmful event was extracted from TxDOT’s CRIS database. Specific data was compiled with respect to vehicle information including injury severity. The relevancy of current longitudinal roadside safety barriers designed for 62 mph oblique impacts is examined by determining whether or not injury severity has increased for real-world vehicle crashes that occurred on higher speed roads, among other factors. At the 5% significance level, the fatal and incapacitating injury severity percentage was not statistically different between 70 mph and ≥ 80 mph for years 2010 – 2013. However, the combined crash data for all four years did show an increase and statistical significance between the percentages at the 5% level. Now that speed limits have generally increased, this preliminary study shows the need for further research into determining impact speeds with updated data to better support the call for revision of MASH impact criteria on posted speed limit roads of ≥ 80 mph.
