Use of Heteroscedastic Ordered Logit Model to Study Severity of Occupant Injury

A heteroscedastic ordered logit model was used to study the effects of various vehicle, environmental, roadway, and occupant characteristics on the severity of injuries sustained by vehicle occupants, conditional on the crash occurrence. As expected, the models found that heavier vehicles increased both a vehicle's crashworthiness and driver aggressiveness toward others. The models also found that if all passenger vehicles were to become 1,000 lb heavier, crash injury outcomes would not change dramatically. However, if all passenger cars were to become light-duty trucks (i.e., minivans, pickups, and sport utility vehicles) of the same weight, incapacitating injuries and fatalities were predicted to rise by 26% and 64%, respectively. Beyond weight and vehicle type, many other factors were controlled for as well. For example, older occupants and female occupants were more likely to experience injury and death, particularly when navigating curved roadway sections with higher speed limits.