The effect of passengers on driver-injury severities in single-vehicle crashes: A random parameters heterogeneity-in-means approach

•Effects of the occupants (both driver and passengers) on driver-injury severities are studied.•A random parameters logit model with heterogeneity in parameter means is used.•The method accounts for possible heterogeneity in the means of the random parameters.•Statistically significant differences exist among sub-populations in the presence/absence of passenger(s).

This paper seeks to investigate the effects of passengers on driver-injury severities. Using single-vehicle crashes, a random parameters logit model with heterogeneity in parameter means is estimated to explore the differences in driver-injury severities in three distinct subgroups; vehicles with one occupant (driver-only), vehicles with two occupants (driver and a passenger), and vehicles with three occupants (driver and two passengers). In addition to considering age, gender and the presence of the passenger(s), a wide range of variables that potentially affect driver-injury severity were considered, including weather conditions, roadway characteristics, vehicle characteristics and driver attributes. Estimation results show that both the age and the gender of the passenger(s) significantly affected driver-injury severities. The findings of this research point toward the need to further study the potentially complex interactions between drivers and passengers.