is there no speed limit on the autobahn
General speed limits in Germany are set by the federal government. All limits are multiples of 5 km/h. There are two default speed limits: 50 km/h (31 mph) inside built-up areas and 100 km/h (62 mph) outside built-up areas. While parts of the autobahns and many other freeway-style highways have posted limits up to 130 km/h (81 mph) based on accident experience, congestion and other factors, many rural sections have no general speed limit. The German Highway Code (Straßenverkehrsordnung) section on speed begins with the requirement which may be rendered in English:
Speed limits in Germany