Comparative Analysis of Injury Severity Resulting from Pedestrian-Motor Vehicle and Bicycle-Motor Vehicle Crashes on Roadways in Alabama

A comparison is provided between the influence of a variety of variables and the injury severities resulting from pedestrian motor vehicle and bicycle motor vehicle crashes in Alabama with the incorporation of the effects of randomness across the observations. Given the occurrence of a crash, random parameter logit models of injury severity with possible outcomes of fatal, major, minor, and possible or no injury were estimated. The estimated models identified a variety of statistically significant factors influencing pedestrian and bicyclist injury severities. According to these models, some variables were found to be significant in only one model (pedestrian or bicycle) but not in the other. For example, variables such as roadway crossing, crashes on Saturdays, and crashes on private roadways were found significant only in the pedestrian model. By contrast, variables such as the use of retroreflective clothing, crashes during the evening peak hour, and crashes in summer were found significant only in the bicyclist model. In addition, some variables-such as older pedestrians and bicyclists, dark roadway, and low-speed roadway-were found significant in both models. Also, estimation findings showed that three parameters in the pedestrian model (between midnight and 7:00 a.m., clear weather, and at intersections) and two parameters in the bicycle model (level grade on tangent and clear weather) could be modeled as random parameters; these findings indicated their varying influences on injury severity. From the results obtained, the effects of different variables on pedestrian and bicyclist injury severities and their possible explanations are discussed.