Registration of vehicle mileage by the Swedish Vehicle Inspection Co. at the time of the annual inspection, since the end of the 1990s, has provided the opportunity for the "annual" mileage driven by groups of vehicles to be estimated. Mileage figures are the key for the estimation of the accident and injury risks of groups of vehicles and for comparison of these. As regards motorcycles, vehicle data concerning age of owner, year model and insurance class have been analysed with respect to motorcyclists injured in traffic and motorcycle mileages for the years 2000, 2001, 2002, 2003 and 2004. In Sweden and internationally, the motorcycle is the mode that has the highest accident risks and, most of all, injury risks in road traffic. Sweden has the additional problem that motorcycles can only be used during the summer months. This means that every year there is a "warming-up period" at the beginning of the new season. As for all motor vehicles, high motorcycle risks are associated with young drivers and limited driving experience, two properties that are strongly coupled. Some researchers want to add to this lack of judgment and little respect for laws and regulations. The age of the driver is today relatively strictly regulated as regards heavy motorcycles, with an engine power of at least 25 kW, which broadly speaking means that the driver must be 21 years old. Those who were automatically allowed to drive a motorcycle with the help of the old driving licence are today almost 50 or older. Traffic safety analysis has been based, inter alia, on the insurance class of the motorcycle which is determined by the relationship between engine power and vehicle weight.