Therefore, in the same way that we inoculate a population against a disease, we can immunise a whole population against road trauma by reducing rates of drink-driving and speeding, and increasing the rates of safety belt and motor cycle helmet wearing. For many individual drivers or passengers, the risks of a collision and death or serious injury are low, and they will choose to drive drunk (or ride with a drunk driver), exceed the speed limit routinely, or not wear a safety belt, without ever being involved in a collision. Their individual experience convinces them that their behaviours are harmless or at least very low risk.