The project focus has been development of guidelines and methods for upper extremity injury reduction in car crashes. The safety of the central body parts improves which indicates the need to develop methods for avoiding non-life threatening injuries such as fracture of the arms. The purpose of the project was to study the injury mechanisms for the upper extremity in car crashes, and the aim has been to propose methods to reduce the injuries. The project focuses on adult occupants inside the vehicles front seat, and frontal and side impacts. The procedure began with understanding and identifying the injury mechanisms. Studies show that most fractures occur on the forearm (radius and ulna) and on the wrists and hands. To determine which injury mechanisms that were most frequent, data were collected from 29 computer simulations with 29 different crash scenarios. The most common kind of impact was the medial part of the wrist in the central part of the instrument panel, combined with the impact of the elbow in the center consol. The results of the simulations created a basis for the method of the component test, with focus on the injury mechanism i.e. the forward movement of the arms into the instrument panel. The component test consisted of a test rig, on which was mounted with a measuring arm of a 50th percentile male dummy. The arm dropped into a block of expanded polypropylene (EPP-block) for observation and study, and with following variable parameters: the impact angle of the surface, velocity and position of the wrist. Then also an instrumented measuring arm from a 5th percentile female dummy was released into an instrument panel. The project contributes to knowledge about the injury mechanism of the upper extremity in car crashes. The most frequent injury mechanism is a forward movement of the arms resulting in an impact with the interior structure of the car. The most frequent injured region is the distal part of the upper extremity. The project has developed and suggested the first step to a test method for the specific injury mechanism. There is a need of more research on how impact angles and velocity affect the violence on the arm.