Speed limits in Germany
In 1973, in the wake of the 1973 oil crisis, a federal speed limit of 100 km/h (62 mph) on Autobahns was imposed to help conserve fuel for fear of impending future shortages (not for environmental or safety reasons). The measure only lasted from December 1973 to March 1974; while the administration and the Bundestag were in favor of keeping the speed limit, the Bundesrat pushed to repeal the law. As a compromise, a "recommended speed" was introduced on Autobahns and "highways outside of built-up areas with a center divide or without a center divide and a continuous lane for overtaking in both directions". This law is basically still in effect today. Unrestricted non-Autobahn highways, however, have since become virtually non-existent or replaced by "Schnellstraßen", Autobahn-like expressways typically limited to 120 or 130 km/h and normally only covering a few kilometers.
Reichsautobahn
The specifications for the autobahns were based on those developed by HAFRABA. They were designed as four-lane limited-access highways, with a central median, road surfaces in each direction normally wide (widened on some major segments immediately before the war), surfaced in concrete. There were no shoulders. In addition to having no intersections, the route was to limit grades as much as possible, to no more than 8%, and curves were to fall within a range of and in radius. One segment just south of Dessau of roughly 10 km in length was designed for speed record attempts (the "Dessauer Rennstrecke") and had six lanes in each direction.