Analysis of injury severity and vehicle occupancy in truck- and non-truck-involved accidents

The impact that large trucks have on accident severity has long been a conc ern in the accident analysis literature. One important measure of accident severity is the most severely injured occupant in the vehicle. Such data ar e routinely collected in state accident data files in the U.S. Among the ma ny risk factors that determine the most severe level of injury sustained by vehicle occupants, the number of occupants in the vehicle is an important factor. These effects can be significant because vehicles with higher occup ancies have an increased likelihood of having someone seriously injured. Th is paper studies the occupancy/injury severity relationship using Washingto n State accident data. The effects of large trucks, which are shown to have a significant impact on the most severely injured vehicle occupant, are ac counted for by separately estimating nested legit models for truck-involved accidents and for non-truck-involved accidents. The estimation results unc over important relationships between various risk factors and occupant inju ry. In addition, by comparing the accident characteristics between truck-in volved accidents and non-truck-involved accidents, the risk factors unique to large trucks are identified along with the relative importance of such f actors. The findings of this study demonstrate that nested legit modeling, which is able to take into account vehicle occupancy effects and identify a broad range of factors that influence occupant injury, is a promising meth odological approach. (C) 1999 Elsevier Science Ltd. All rights reserved.