Road speed limits in the United Kingdom

Road speed limits in the United Kingdom are used to define the maximum legal speed (which may be variable) for vehicles using public roads in the UK, and are one of the measures available to attempt to control traffic speeds. The speed limit in each location is indicated on a nearby traffic sign or by the presence of street lighting. Signs show speed limits in miles per hour (mph) or use the national speed limit (NSL) symbol.

The speed limit is 70 mph on motorways, 70 mph on dual carriageways, 60 mph on single carriageways and 30 mph in areas with street lighting (restricted roads). These limits may be reduced by roadside signs and apply to cars, motorcycles, car-derived vans up to 2 tonnes maximum laden weight (MLW), and to motorhomes or motor caravans not more than 3.05 tonnes maximum unladen weight. Other classes of vehicles are subject to lower limits on some roads.

Speed limits in the UK are used to define maximum desirable traffic speeds for the purposes of road safety (to reduce the number of road casualties), to reduce negative environmental impacts of traffic, to increase fuel use efficiency and to satisfy local community wishes.

Enforcement of UK road speed limits was traditionally done using police 'speed traps' set up and operated by the police who now increasingly use speed guns, automated in-vehicle systems and automated roadside traffic cameras. Some vehicle categories have various lower maximum limits enforced by speed limiters.

Ever since they have been introduced, speed limits have been controversial. They have either been opposed or supported from various sources; including motoring advocacy groups, anti-motoring groups and others who either consider them to be irrelevant, set too low or set too high.

...
Wikipedia