The Indiana Department of Transportation (INDOT) has installed guardrail systems on interstate highways and other highways in accordance with a variety of standards throughout the years. Traffic volume has increased and the posted speeds have been raised on most INDOT’s interstate highways. Consequently, the characteristics of run-off-the-road (ROR) crashes may have changed. In the meantime, material prices have increased considerably and the guardrail maintenance and crash repair costs have increased accordingly. There is no doubt all these changes will not only greatly affect the ROR crash prediction, but also greatly affect the guardrail benefit/cost analysis. This study examined the current use of roadside guardrails on INDOT intestates, State highways, and US highways, roadways, including types and lengths of guardrails, types and numbers of guardrail end treatments, and field guardrail positions. Based on the records of total 4657 ROR crashes occurred in 2004 and 2006, this study investigated the characteristics of ROR crashes, such as frequencies and locations of ROR crashes, crash consequences (number of vehicles involved, injuries and fatalities), and the effects of main factors, in particular roadway geometrics, seasons and traffic volume, on the highways of different classes. Furthermore, this study investigated the features of vehicle-guardrail crashes, including impact positions and corresponding frequencies and consequences. ROR crash predictions were examined in all aspects in this study, including encroachment rates, crash probabilities, and severity probabilities. It was found that the encroachment rates obtained by this study are less than those in the AASHTO Roadside Design Guide. This study evaluated the issues associated with the guardrail crash repair costs, such as parts costs, labor costs, and equipment costs.
