Researchers have always had great interest in traffic safety and the phenomenon of motor vehicle crashes (MVCs). Though scores of service members are severely injured or killed in off-duty MVCs each year, few studies have addressed the MVC phenomenon within the military population and none have conducted a comprehensive evaluation of the causal factors associated with MVCs involving military personnel. The main purpose of this dissertation was to gain a greater understanding of the causal factors associated with serious and fatal off-duty personal MVCs for military service members with the ultimate goal of preventing future losses. The HFACS-MVC framework was developed based on the established human error framework HFACS and used to classify causal factors from archival narratives from Class A and B off-duty MVCs in the USAF, USN, and USMC. This study identified the human factors trends associated with off-duty military MVCs and compared main trends for four variables of interest, specifically for military branch, vehicle type, paygrade, and age group. The main human factor trends associated with off-duty MVCs were skill based technique errors related to negotiating curves/turns and regaining road positions and procedural violations related to speeding and drunk driving. Significant differences were found between human factors trends associated with MVCs for both vehicle type and military branch. For vehicle type, the human factors trends for 4W MVCs were significantly different from those for 2W MVCs, especially at the preconditions level. However, for military branch, the human factors trends suggest differences in the investigation and reporting processes for the three branches
