Speed limit

Road speed limits are used in most countries to set the maximum (or minimum in some cases) speed at which road vehicles may legally travel on particular stretches of road. Speed limits may be variable and in some places speeds are unlimited. Speed limits are normally indicated on a traffic sign. Speed limits are commonly set by the legislative bodies of nations or provincial governments and enforced by national or regional police and / or judicial bodies.

The first maximum speed limit was the 10 mph (16 km/h) limit introduced in the United Kingdom in 1861. The highest posted speed limit in the world is 140 km/h (87 mph), which applies to some roads in Poland and Bulgaria; similarly Texas posts 85 mph (137 km/h) on one 40-mile (64 km) long toll road. However, some roads have no speed limit for certain classes of vehicles. Best known are Germany's less congested Autobahns and areas of Australia's Stuart Highway. where automobile drivers have no mandated maximum speed; measurements from the German State of Brandenburg in 2006 showed average speeds of 142 km/h (88 mph) on a 6-lane section of autobahn in free-flowing conditions. Rural areas on the Isle of Man, the Indian states of Andhra Pradesh,Maharashtra, and Telangana, also lack speed limits, but speeds are lower when measured on those lower design roads.

National Maximum Speed Law

The National Maximum Speed Law (NMSL) in the United States was a provision of the Federal 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than 55 miles per hour (90 km/h). It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis.

While Federal officials hoped gasoline consumption would fall by 2.2%, actual savings were estimated at between 0.5% and 1%.

The law was widely disregarded by motorists, and most states opposed the law. Actions ranged from proposing deals for exemption to de-emphasizing speed limit enforcement. The NMSL was modified in 1987 and 1988 to allow up to 65 mph (105 km/h) limits on certain limited access, rural roads. Congress repealed the NMSL in 1995, fully returning speed limit setting authority to the states.

The law's safety benefit is disputed as research found conflicting results.

History

Historically, the power to set speed limits belonged to the states. Immediately before the National Maximum Speed Law became effective, speed limits were as high as 75 mph (120 km/h). (Kansas had lowered its turnpike speed limit from 80 before 1974.) Montana and Nevada generally posted no numeric speed limit on rural roads.