Variable categories influencing single-vehicle run-off-road crashes and their severity

Abstract

Single-vehicle run-off-road (ROR) crashes account for a significant number of all the single-vehicle crashes and all the fatalities in the United States. The variable categories influencing single-vehicle ROR crashes and their severity could be different from other single-vehicle crashes. This paper, therefore, focuses on investigating single-vehicle ROR crashes to identify and compare variable categories influencing their occurrence and severity. A logistic regression model was developed to evaluate and identify variable categories associated with single-vehicle ROR crashes compared to other single-vehicle crashes. The results indicate that variables such as road characteristics (number of lanes, road surface condition, road terrain, functional classification, and geometric condition), weather condition, road lighting condition, vehicle type, and, driver characteristics (driver physical condition, age, and gender) are observed to have a statistically significant influence on the occurrence of single-vehicle ROR crashes. A partial proportionality odds model was developed to evaluate and identify variable categories associated with injury severity of single-vehicle ROR crashes. The results indicate that variables and variable categories such as weather condition (cloudy and rain), speed limit (<= 40.2 kmph [25 mph] and > 88.5 kmph [55 mph]), vehicle type (primarily buses), drivers’ age (<= 18 years), road surface condition (presence of water, ice, snow, and slush), and, mountainous terrain condition are observed to have a statistically significant influence on single-vehicle ROR crash severity.