Severity indices for motorcyclist collisions with roadside hazards and barriers

Roadside barriers are often deployed between road users and fixed hazards to protect users from injury. However, the Australian Roadside Design Guide (ARDG) does not consider motorcyclists in the risk-based decision process for the deployment of a barrier, since the severity indices for barriers and fixed hazards were developed for passenger vehicles. The provision of a safe road environment for all road users, including motorcyclists, is an objective of all road authorities, and is the basis of the Safe Systems approach. Therefore, there is a need to determine the risk of injury to motorcyclists from fixed objects and barriers, and to provide guidance to roadside designers. The aim of the present study is to develop severity indices for motorcyclists applicable to the ARDG. The study used a retrospective case series methodology, using linked police-reported road crash and hospital admission data in New South Wales, from 2001 to 2009. A total of 1,364 motorcyclists injured as a result of single-vehicle collisions with roadside barriers, trees, utility poles and other fixed roadside infrastructure were identified. Serious injury rates and logistic regression were used to develop severity indices and calculate relative risks of trees, posts, utility poles and roadside barriers to motorcyclists. It is shown that roadside barriers are generally safer for motorcyclists than the hazards that they shield. The methodology used for developing the severity indices was aligned with that used for passenger vehicles recently developed by other authors, such that a consistent approach may be proposed for the ARDG.