Injury is a leading cause of death, hospitalisation and disability world-wide. The World Health Organization predicts that unintentional injuries arising from road traffic incidents will rise to take third place in the rank order of international disease burden by the year 2030. Although these statistics and the associated economic costs are staggering, the effect of unintentional injury and death from trauma is more apparent, and more disturbing, when seen personally. By a young age, nearly everyone in the world, regardless of region, wealth or education, has had a relative or someone that they know killed or disabled in an "accident". The quality of life and financial effects on the injured person and their families and friends are plainly evident and clearly devastating. Many unintentional injuries are in reality not accidents; they could be prevented with changes in policy, education, or through improved safety devices. Arrayed against these preventable injuries, a diverse group of injury prevention researchers and practitioners work to decrease the incidence of unintentional injury. In trauma biomechanics, the principles of mechanics are used to understand how injuries happen at the level of the bones, joints, organs and tissues of the body. This knowledge is central in the development, characterization and improvement of safety devices such as helmets and seat belts and in the safe design of vehicles and equipment used for transportation, occupation and recreation.