  This paper investigates factors affecting injury severity of crashes
involving trucks for different lighting conditions on rural and urban roadways.
It uses 2009-2013 Ohio crash data from the Highway Safety Information System.
The explanatory factors include the occupant, vehicle, collision, roadway,
temporal and environmental characteristics. Six separate mixed logit models
were developed considering three lighting conditions (daylight, dark, and
dark-lighted) on two area types (rural and urban). A series of log-likelihood
ratio tests were conducted to validate that these six separate models by
lighting conditions and area types are warranted. The model results suggest
major differences in both the combination and the magnitude of impact of
variables included in each model. Some variables were significant only in one
lighting condition but not in other conditions. Similarly, some variables were
found to be significant in one area type but not in other area type. These
differences show that the different lighting conditions and area types do in
fact have different contributing effects on injury severity in truck-involved
crashes, further highlighting the importance of examining crashes based on
lighting conditions on rural and urban roadways. Age and gender of occupant
(who is the most severely injured in a crash), truck types, AADT, speed, and
weather condition were found to be factors that have significantly different
levels of impact on injury severity in truck-involved crashes.
