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.
Dual carriageway
"Autobahnähnliche Straßen" mostly are colloquially referred to as "gelbe Autobahn" (yellow motorway) because they have the same technical standard as the "Autobahn" but have black on yellow signs instead of the white on blue signs used on the "Autobahn" motorway network. These are generally high-speed arterial roads in larger cities or important roads within a federal state that do not connect to major cities, so that they do not fall under the federal budget for the "Autobahn" network. The federal road Bundesstraße 27 is an example where about half of its length is upgraded to a high speed motorway standard. On the basis of their structure these roads have, comparable to the German "autobahn", the legal foundation that no default speed limit exists (design speed 130 km/h), although the standard advisory speed limit () still exists. Nevertheless expressways are often given speed limit signs.
At the moment some (blue) motorways have been taken out of the "Autobahn" network programme but still have the blue signs; and on the other hand some former non-"Autobahn" (yellow) motorways have been added to "Autobahn" budgeting but the signs have not been changed either. Motorways that are neither in the "autobahn" network nor in the "Bundesstraße" network are given black on white signs, following the same sign code as high-speed dual carriageways—this is mostly seen on urban trunk roads.