A Spatial Generalized Ordered Response Model to Examine Highway Crash Injury Severity
Abstract
This paper proposes a flexible econometric structure for injury severity analysis at the level of
individual crashes that recognizes the ordinal nature of injury severity categories, allows
unobserved heterogeneity in the effects of contributing factors, as well as accommodates spatial
dependencies in the injury severity levels experienced in crashes that occur close to one another
in space. The modeling framework is applied to analyze the injury severity sustained in crashes
occurring on highway road segments in Austin, Texas. The sample is drawn from the Texas
Department of Transportation (TxDOT) crash incident files from 2009 and includes a variety of
crash characteristics, highway design attributes, driver and vehicle characteristics, and
environmental factors. The results from our analysis underscore the value of our proposed model
for data fit purposes as well as to accurately estimate variable effects. The most important
determinants of injury severity on highways, according to our results, are (1) whether any vehicle
occupant is ejected, (2) whether collision type is head-on, (3) whether any vehicle involved in
the crash overturned, (4) whether any vehicle occupant is unrestrained by a seat-belt, and (5)
whether a commercial truck is involved.