In 1995, North Carolina ranked 9th of the 50 states in terms of total highway-related deaths. During that year, 1,418 people died on the State's highways. In response to these trends in traffic deaths, the State DOTs of Region IV and the FHWA wanted to better understand and prevent fatal crashes and their causal factors. The Causal Chain Analysis provided herein reviewed the chain of events of 150 fatal crashes. Then, each fatal crash was studied to see what effect select safety treatments would have had on the outcome of the crash. Causal chain analysis aims to determine if the treatment would have ""broken the chain."" By breaking the ""chain"" then the fatal crash would have been either prevented altogether or at least have been limited in severity.
The main objectives of this study are:
- To complete the North Carolina portion of the casual chain analysis for the regional
- pooled fund study for a sample of fatal crashes [Georgia Institute of Technology, Pooled fund study no. SPR-3 (057) "Investigation and Identification of Principal Factors Contributing to Fatal Crashes in the Southeastern United States"]
- To develop a ranked comprehensive list of candidate countermeasures likely to be effective for reducing both the number and severity of fatal crashes on two-lane rural roads in North Carolina.
This list will include countermeasures ranked according to their expected influence on fatal crash frequency and severity for two-lane rural roads. The list will be based upon the findings of casual analyses of actual fatal crashes.
The application of the findings of this study may be tempered because the crashes were a subset of all reported crashes. These crashes included 150 randomly selected rural two-lane fatal crashes reported in North Carolina in 1997.
The recommended next step would be to find areas where the countermeasures may be applied. One such method would be to develop warranting criteria in the Highway Safety Improvement Program (HSIP) to identify locations where these countermeasures may be applied. However, it is recommended to expand the data to multiple years and to all reported crashes.
This list includes countermeasures ranked according to their expected influence on fatal crash frequency and severity for two-lane rural roads.
Another opportunity to apply the results of this project is in the driveway permit process and requirements. Since the traversable drainage structure countermeasure, D 3f, had the highest crash modification factor, it would be reasonable to require new driveways to be constructed so that they are traversable. This should include all new driveways, including residential driveways. This recommendation combined with a HSIP warrant to identify and treat potentially hazardous locations could reduce the risk of fatal crashes on rural two-lane roads.
Currently, NCDOT does not have a complete list of crash reduction factors for all countermeasures implemented. This process can be modified and used to develop a more complete list of crash modification factors. Since the process has already been developed through this project, the only components needed to apply this methodology to other situations are the crash selection process. Once the crash reduction process is developed, then the engineers would complete the same process and analyses that were used in this project. The resulting product would be a more complete list of crash reduction factors that NCDOT could use to help prioritize safety projects.
The last recommendation includes developing HSIP warranting criteria and working with the Governor's Highway Safety Program (GHSP) and law enforcement agencies to target speed enforcement. Such targeted programs could help identify locations and times where there are higher incidents of speed related crashes.
This study reviewed only a select number of countermeasures and it would be preferable to evaluate more countermeasures than the 30 identified. However, the cost of developing the additional countermeasures prevented adding additional countermeasures in this study. If a similar program became standard practice during the review of all fatal crashes, then over time, a robust source of information concerning fatal crashes in North Carolina could be developed.
