From a detailed reconstruction of each of the cases with severe injury, the authors found that none of the occupants sustained the serious injury during the initial barrier impact.PMCID: PMC3242556 PMID: 21050605 Secondary Collisions Following a Traffic Barrier Impact: Frequency, Factors, and Occupant Risk Douglas J.
Impact Vehicle Library License Information DisclaimerGabauer Author information Copyright and License information Disclaimer Bucknell University Copyright Association for the Advancement of Automotive Medicine AAAM 2010 Abstract This study has investigated secondary collisions following an initial barrier impact in tow-away level crashes.
The analysis included 2026 barrier impact cases that were selected from 12-years of in-depth crash data available through the National Automotive Sampling System (NASS) Crashworthiness Data System (CDS). Secondary collisions were found to occur in approximately one-third of tow-away level crashes where a traffic barrier was the first object struck. Secondary crashes were found to primarily involve an impact to another vehicle, an impact to another barrier, or a rollover; tree and pole impacts were found to represent a much smaller proportion of secondary impacts. Through a detailed analysis of vehicle trajectory, this study supports previous research suggesting secondary collision risk is substantial even for vehicles not ultimately involved in a secondary collision. Compared to a single barrier impact, the occurrence of a secondary collision was found to increase the risk of serious occupant injury by a factor of 3.5, equivalent to the serious injury risk difference found between a belted and unbelted occupant in a traffic barrier crash. INTRODUCTION A longitudinal traffic barrier redirects an impacting vehicle in order to prevent it from colliding with a more dangerous roadside object. Ideally, the impacting vehicle should come to rest alongside the barrier to minimize the risk of a secondary collision. Examples of a secondary collision would include, but are not limited to, a vehicle being redirected into an adjacent traffic lane and impacting another vehicle or a vehicle impacting a tree following the initial barrier impact. Previous real-world crash analysis has revealed that these secondary impacts are not uncommon and, when they occur, result in a greater risk of fatal and severe occupant injuries. Although full-scale crash test evaluation procedures attempt to address post-impact vehicle trajectory, it is rarely a discerning factor in the assessment of traffic barrier crash performance. Further, investigation of this issue has been limited to studies conducted over 20 years ago and only at the state, not the national, level. OBJECTIVE The purpose of this study is to investigate secondary collisions following an impact with a traffic barrier with more recent national level data to determine (1) the frequency of these crashes, (2) the resulting influence on occupant injury, and (3) how factors, such as barrier type and vehicle type, affect the occurrence and severity of these crashes. Impact Vehicle Library Series Of FullBACKGROUND AND PREVIOUS RESEARCH Longitudinal barriers, such as w-beam guardrails, must demonstrate adequate crash performance in a series of full-scale crash tests prior to being considered acceptable for use on the national highway system. Impact Vehicle Library Update To TheProcedures for determining the crashworthiness of longitudinal barriers in the US are set forth in the Manual for Assessing Safety Hardware ( AASHTO, 2009 ), which is a recent update to the procedures set forth in the National Cooperative Highway Research Program (NCHRP) Report 350 ( Ross et al., 1993 ). Analogous European crash test procedures are prescribed in EN-1317 ( CEN, 1998 ). These test procedures specify high speed oblique angle impacts into a barrier with both a passenger car and a large pickup truck. The results of the tests are evaluated against specific criteria in three areas: (1) the structural adequacy of the barrier, (2) the potential for injury to vehicle occupants, and (3) the vehicle trajectory as a result of the impact. The longstanding US criteria for post-impact vehicle trajectory was a recommendation that the vehicle exit the barrier at an angle less than 60 percent of the impact angle and that the vehicle not intrude into adjacent traffic lanes ( Ross et al., 1993 ). Although quantitative, this recommendation was simply a preferable condition and not a strict requirement for a passing barrier crash test. It should be noted, however, that the recently updated criteria do require that a vehicle exit the barrier within an exit box of specified dimensions dependent on vehicle length and width ( AASHTO, 2009 ). A small number of previous studies have investigated the issue of post-impact vehicle trajectory using real-world crash data. Ray et al. (1986) examined 679 barrier crashes: 124 crashes from a Texas bridge rail study and 555 crashes from the Longitudinal Barrier Special Study (LBSS). Of the available data, only 17 cases, or less than 3 percent, were found to result in serious or severe occupant injury. More than 80 percent (14 of 17) of these crashes involved a secondary collision.
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