Bundesstraße
One distinguishing characteristic between German "Bundesstraßen" and "Autobahnen" is that there usually is a general 100 km/h (62 mph) speed limit on federal highways out of built-up areas, as opposed to the merely advisory speed limit ("Richtgeschwindigkeit") of 130 km/h (83 mph) in unmarked sections of the autobahns. However, a number of "Bundesstraßen" have been extended as expressways (dual carriageways) (colloquially called "Yellow Autobahns"). Many of these have speed limits of usually 100–120 km/h, others have only an advisory speed limit like autobahns. Most sections of the federal highways are only single carriageway with one lane for each direction and no hard shoulder pull-out area.
Autobahn
However, after the crisis eased in 1974, the upper house of the German parliament, which was controlled by conservative parties, successfully resisted the imposition of a permanent mandatory limit supported by Chancellor Brandt. The upper house insisted on a recommended limit until a thorough study of the effects of a mandatory limit could be conducted. Accordingly, the Federal Highway Research Institute conducted a multiple-year experiment, switching between mandatory and recommended limits on two test stretches of autobahn. In the final report issued in 1977, the Institute stated the mandatory speed limit could reduce the autobahn death toll but there would be economic impacts, so a political decision had to be made due to the trade-offs involved. At that time, the Federal Government declined to impose a mandatory limit. The fatality rate trend on the German autobahn mirrored those of other nations' motorways that imposed a general speed limit.