German "Autobahnen" are widely known for having no federally mandated speed limit for some classes of vehicles. However, limits are posted (and enforced) in areas that are urbanised, substandard, accident-prone, or under construction. On speed-unrestricted stretches, an advisory speed limit () of applies. While driving faster is not illegal as such in the absence of a speed limit, it can cause an increased liability in the case of a collision (which mandatory auto insurance has to cover); courts have ruled that an "ideal driver" who is exempt from absolute liability for "inevitable" tort under the law would not exceed "Richtgeschwindigkeit".