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.