ABSTRACT
Motorcycle users are one of the vulnerable road users in the event of a crash due to the low level of protection. In most of the studies related to the safety of motorcycle, the highest level of occupants' injury severity is frequently taken into account, which involves one aspect of the crash. To conduct a comprehensive study of crash severity, accident size can be utilized, which consists of different aspects of a crash. Therefore, to investigate the influential factors on the accident size of motorcycle-involved crashes, structural equation modeling was used in the present study. Results reveal that the crashes involving heavy vehicles, old-aged drivers, female drivers, day time, dry road surface, two-way roads, lack of shoulder and rural roads are associated with larger accident size. This study also showed the importance of considering the driver and road characteristics in safety programs for mitigating the crash severity.