The Analysis of the Influence of Occupants’ Characteristics on Crash Severity Based on the Mixed Linear Model

To investigate and quantify the influencing factors of highway traffic crashes, as well as to thoroughly examine the impact of occupants’ characteristics on crash severity, 15 independent variables were extracted from four aspects, including people, vehicles, roads, and environment, and defined as 15 indicators using the method of processing categorical variables. General linear analysis and the generalized linear mixed model were used to investigate crash aggregation and build a highway crash severity impact model using the crash data of California highways. Findings show that factors including the number of vehicles involved in a crash, type of crashes, type of vehicles, and lighting significantly impact the severity of a collision with hierarchical aggregation. The severity of highway crashes is influenced considerably by the driver’s age, gender, physical condition, the severity of injuries to the occupants, seat position, safety precautions, and other occupants’ variables.