Identification of Causal Factors and Potential Countermeasures for Fatal Rural Crashes

Project summary:

Developing effective strategies for achieving a zero-fatality goal requires understanding the exact causes of traffic crashes. This project addresses the issue of causation first by reconstructing a set of run-off road crashes, and determining if the presence of barriers compliant with NCHRP 350 Test level 3 would have prevented the crashes, and second by conducting an expert assessment of the presence of specified causal factors (and susceptibility to countermeasures) for a larger sample of fatal rural crashes. This project was divided into three phases. In Phase One, ten fatal run-off-road crashes were reconstructed from crash scene diagrams and investigation reports. Evidence of excessive speed was found in five of these, and a failure to properly use seatbelts in eight of the ten. For seven of these crashes, analysis indicates that barriers complying with Test Level 3 of NCHRP Report 350 would probably have stopped the crashing vehicle's encroachment. In Phase Two, a vehicle trajectory simulation model was developed and used to reconstruct five fatal median-crossing crashes. Clear evidence of excessive speed was found in one of these, and in three of the five the encroaching vehicle would probably have been restrained by barriers compliant with Test Level 3. In Phase Three, five teams of traffic safety professionals reviewed accident reports from a sample of fatal rural crashes, with the aim of identifying possible causal factors and potential countermeasures. The most frequently identified causal factors were driver inexperience and failure to properly use restraints, while provision of rumble strips, improvements to roadsides or cross-slopes, and provision of guardrails or barriers were the most frequently-cited countermeasures.