all national speed limits, seeing them as Nazi relics, reverting to State-level decisions. National limits were reestablished incrementally. The urban limit was enacted in 1956, effective in 1957. The limit on rural roads—except autobahns—became effective in 1972. Oil crisis of the 1970s Just prior to the 1973 oil crisis, Germany, Switzerland, and Austria all had no general speed restriction on autobahns. During the crisis, like other nations, Germany imposed temporary speed restrictions; for example, on autobahns effective 13 November 1973. Automakers projected a 20% plunge in sales, which they attributed in part to the lowered speed limits. The 100 km/h limit championed by Transportation Minister Lauritz Lauritzen lasted 111 days. Adjacent nations with unlimited speed autobahns, Austria and Switzerland, imposed permanent limits after the crisis. 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. Environmental concerns of the 1980s In the mid-1980s, acid rain and sudden forest destruction renewed debate on whether or not a general speed limit should be imposed on autobahns. A car's fuel consumption increases with high speed, and fuel conservation is a key factor in reducing air pollution. Environmentalists argued that enforcing limits of limit on autobahns and on other rural roads would save lives as well as the forest, reducing the annual death toll by 30% (250 lives) on autobahns and 15% (1,000 lives) on rural roads; the German motor vehicle death toll was about 10,000 at the time. The federal government sponsored a large-scale experiment with a speed limit in order to measure the impact of reduced speeds on emissions and compliance. Afterward, again, the