Although the prime objective is accident prevention, the second objective is injury prevention in case of an accident.
To be able to design effective counter measures one has to know what parts of the body are injured and what injury mechanism is responsible for the injury.
The events before and during an accident can be very complex. The rider of the PTW may take action to avoid the accident. This may change the trajectory and speed of the PTW and its rider. A collision with a car or other object will again change these and eventually parts of the body of the rider may hit some parts of his own PTW, of another vehicle or of another object. The nature and severity of the injuries depend on how these parts hit each other (which speed and angle).
The standard accident reports contain little information on injuries. Detailed information on the events before and during the accident can only come from in-depth studies at the scene of the accident and from inspection of vehicles and objects involved in the accident as well as from medical examination of the casualties. As a consequence the sample of an in-depth study is usually small, includes few severe injury cases and is regional rather than national; relatively few such studies exist.
In-depth studies show that injuries to the legs are frequent, but injuries to the head are more severe even though wearing a helmet. Head injuries would have been much more frequent if helmets had not been worn. Collisions between the front of the PTW and the side of a car are frequent, with many riders falling before the collision as well as many riders departing from the PTW during the collision. Injuries from single vehicle accidents are more severe when hitting a fixed object.
Special attention is paid to the injuries as a result of a rider colliding with a guard rail. The injuries as a result of a collision with a guard rail are influenced by the design of the guard rail. More injuries result from hitting the rail post than from impact with the rail itself. Little is known about differences in injury mechanisms between types of PTW, between different traffic conditions or about accidents with more severe injuries.