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.
Speed limits are one of the measures available to attempt to control traffic speeds, reduce negative environmental effects of traffic, increase fuel use efficiency and satisfy local community wishes. 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 the national speed limit (NSL) sign may be used.
The national speed limit is 70 mph (113 km/h) on motorways, 70 mph (113 km/h) on dual carriageways, 60 mph (97 km/h) on single carriageways and generally 30 mph (48 km/h) (20 mph (32 km/h) in Wales) in areas with street lighting (Built-up area). These limits may be changed by road 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 long tons (3.05 tonnes) maximum unladen weight. Other classes of vehicles are subject to lower limits on some roads.[1]
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 are both 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.
Default maximum speed limits apply to all roads where no specific lower numeric speed limit is already in force. The default speed limit is known as the national speed limit (NSL). The NSLs vary by road type and for vehicle types.[2][3]
In Northern Ireland only, vehicles displaying L-plates (for learner drivers) or R-plates (for newly qualified drivers) may not exceed 45 mph (72 km/h), regardless of whether the driver is required to display them. This restriction does not apply to goods vehicles, buses and coaches displaying L-plates while driving on a motorway, or to motorcycles of Class A2 or A displaying R-plates.[4]
Some classes of vehicles are required to have speed limiters which enforce a maximum speed by physical means.[5] New vehicles should be fitted with limiters as follows:
The law also stipulates retrofitting of limiters to older buses and HGVs, mostly at the above speeds, with two minor variations allowing "70 mph" (technically, 112 km/h) for some older buses, and "60 mph" (96.5 km/h) for a limited selection of HGVs between 7.5 and 12 tonnes. Some older mopeds may be restricted instead to either 30 mph or 50 km/h (31 mph), although the accuracy and reliability of the restriction methods used is variable.
Some other vehicles, especially light commercial or service vehicles, may be voluntarily fitted with limiters by their owners (either private businesspeople or company fleets), generally set to various speeds between 90 km/h (56 mph) and 70 mph (113 km/h), though some mostly-citybound service and delivery vehicles may be limited to 50 mph (80 km/h) or less. Likewise, some heavy goods vehicle operators choose to limit to 85 km/h (53 mph) or 80 km/h (50 mph) for fuel saving. In all cases, a warning sticker must be displayed on the rear of the vehicle.
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The Department for Transport encourages the use of either '20 mph (32 km/h) speed limits' or '30 mph (48 km/h) speed limit zones' in urban situations where vulnerable road users are at particular risk.[6]
In 1998 the TRL reported[7] that signed 20 mph (32 km/h) speed limits only reduced traffic speeds by about 1 mph (1.6 km/h) and delivered no discernible reduction in accident numbers but that 20 mph (32 km/h) zones achieved average speed reductions of 10 mph (16 km/h) with child pedestrian accident reductions of 70% and child cyclist accident reductions of 48%.[8] The report noted that the cost of wide area traffic calming was prohibitive.
20 mph (32 km/h) speed limits are based on signage alone and are used where 85th percentile speeds are already below 24 mph (39 km/h).[6]
A report published in 2010 by the Department for Transport regarding Portsmouth City Council's 20 mph (32 km/h) speed limit on 255 mi (410 km) of the city's 272 mi (438 km) of roads found a small 1.3 mph (2.1 km/h) reduction in traffic speed and a small 8% increase in the number of serious accidents – neither of which were statistically significant – and a 21% reduction in the number of accidents. There was a 6% increase in the numbers killed or seriously injured (KSI) – also not statistically significant due to the small numbers involved – and a 22% reduction in the total number of road casualties.[9]
In places where 20 mph (32 km/h) speeds are desired but where excessive speeds (85th percentile speed of 24 mph (39 km/h) or above) occur, 20 mph (32 km/h) zones are recommended. These have to use traffic calming measures to reduce speeds to below 20 mph (32 km/h).[10]
A report published in 2008 estimated that following the introduction of 20 mph (32 km/h) zones in London, a reduction of casualties by 45% and KSI by 57% occurred.[11]
On 17 September 2023, Wales introduced a default speed limit of 20 mph (32 km/h) in built up areas. An estimated 7,700 miles (12,400 km) of the 22,000 miles (35,000 km) of road in the country was changed from a 30 mph (48 km/h) to a 20 mph (32 km/h) speed limit, with local authorities allowed to apply for exemptions to the new law.[12] Following its introduction, only an estimated 3% of the total road network in Wales remains at 30 mph (48 km/h), as opposed to 37% before the change.[13] The Welsh Government said they were doing this to reduce death and injury on the roads, as well as reduce noise and pollution and encourage active travel. This was despite their own figures showing the measure could cost Wales £4.5 billion over a 30 year period.[12] Spain had already enacted a similar default speed limit in 2019. Across the UK, many cities and towns already had residential areas with 20 mph (32 km/h) speed limits. Scotland were considering a similar 20 mph (32 km/h) default speed limit to Wales.[12]
Research carried out for the Department for Transport, to provide supporting evidence for Local Transport Note 1/11 on shared space, showed that in all of the ten shared space sites that were studied, that although they all had speed limits of 30 mph (48 km/h), that the average speeds on them was around 20 mph (32 km/h).[14]
Speed limit road signs are used to inform road users where speed limits other than the applicable national speed limit apply.
Variable speed limits are used on some major traffic roads. These can be changed in response to weather, traffic levels, time of day or for other reasons with the currently applicable speed limit displayed using an electronic road sign. Signs with the speed shown in a red circle are compulsory, signs where the speed is not within a red circle are advisory and exceeding these speeds while driving safely within the applicable national speed limit is not in itself an offence.[15] Variable speed limits were introduced on some congested major routes as an element of controlled motorway techniques to improve traffic flows for given prevailing conditions.[16]Part-time variable speed limits may also be used outside schools.[citation needed]
Rarely, minimum speed limits are used, such as through the Mersey Tunnels, to maintain free flow and safe passage through otherwise hazardous or enclosed areas.[17] Circular blue signs with white numbers indicate the start of these limits, and similar signs with a red diagonal line indicate their end.[18] Contrary to popular belief, there is no minimum speed limit on motorways, although certain classes of slow vehicles (as well as those of any class that cannot maintain 25 mph (40 km/h) on the level whilst unladen) are prohibited on safety grounds and drivers are expected to not cause unnecessary obstruction by driving unusually slowly.
According to the government, speed limits are used to help achieve appropriate traffic speeds for safety, and environmental and accessibility reasons.[19] The Department for Transport state that "speed limits play a fundamental role" in the effective management of traffic speeds in relation to the safety of both drivers and all other road users.[20]
The 30 mph (48 km/h) speed limit in built-up areas was introduced in 1934 in response to high casualty levels.[21] The 70 mph (113 km/h) limit on previously unrestricted roads was introduced in 1965 following a number of serious motorway accidents in fog earlier the same year.[22]
The Department for Transport believes that effective speed management involves many components but that speed limits play a 'fundamental role' and are 'a key source of information to road users' particularly as an indicator of the nature and risks posed by that road to both themselves and other motorised and non-motorised road users.[20]
The Parliamentary Select Committee for Transport Safety published a report entitled 'The Ending the Scandal of Complacency' in 2007 which highlighted how casualty levels rise with increasing speed and recommended reducing speed limits on streets with high pedestrian populations and on dangerous rural roads. The report highlights that when two cars crash head-on at 60 mph (97 km/h) a driver has a 90% chance of dying which falls to 65% at 50 mph (80 km/h). While recommending 20 mph (32 km/h) speed zones the committee noted that these zones 'should not rely on heavy-handed enforcement measures'.[23]
In 2008 14% of collisions reported to the police had a speed-related contributory factor (either "exceeding the speed limit" or "travelling too fast for conditions") reported rising to 24% for fatal accidents and 25% of all road deaths.[n 2] "Exceeding the speed limit" was reported as a contributory factor in 5% of collisions and 14% of fatal collisions. "Travelling too fast for conditions" (but within the prevailing speed limit) was recorded as one of the contributory factors in a further 8% of all collisions (and 9% of all fatal, 9% of all serious and 8% of all slight accidents),[n 3]
The UK government publishes Reported Road Casualties Great Britain (RRCGB) each year, based on road traffic casualties data (STATS19) reported to the police, which has been collected since 1949, and with additional data going back to 1926.[24] The highest number of road fatalities recorded in a single year in GB was 9,196 in 1941.[n 4] The highest number of fatalities during peacetime was 7,985 for 1966,[n 5] following the introduction of the national 70 mph (113 km/h) speed limit in 1965 and the year before the legal drink drive limit and the associated Breathalyzer laws were introduced.
The 2009 edition also summarised the characteristics of speed related fatal collisions as typically occurring on unclassified rural 60 mph (97 km/h) speed limit roads, the driver being a male under the age of 30, with the collision types being head-on, lost control or cornering and the cause being loss of control whilst cornering or overtaking and the contributory factors being excess or inappropriate speed, loss of control, aggressive, careless or reckless behaviour or in a hurry.[n 6]
Speed limits are also used where reduced vehicle speeds are desired to help reduce vehicle emissions and traffic noise, and to improve the accessibility conditions for more vulnerable road users such as pedestrians and cyclists and to reduce the perceived traffic risk for local people.[25]
During the 1973 oil crisis a temporary maximum national speed limit of 50 mph (80 km/h) was introduced on all roads, including motorways to reduce fuel consumption, which was later progressively raised on Motorways (to 70 mph (113 km/h)) and dual carriageways (to 60 mph (97 km/h)), before a final change to single and dual carriageway non-motorway roads that produced the current NSL situation.[26]
Parliament estimates that "Most drivers and pedestrians think speeds are generally too high but 95% of all drivers admit to exceeding speed limits".[27] DfT guidance makes it clear that setting speed limits in isolation, or setting ones that are "unrealistically low" may be ineffective and lead to disrespect for the speed limit.[28] Bath and North East Somerset Council say that speed limits on their own do not necessarily reduce traffic speeds and should be supported by enforcement to target "irresponsible drivers" or traffic calming.[25]
In the UK, in 2017 the average free flow speed for each vehicle type is correlated with the applicable speed limit for that road type and for motorways and national speed limit single carriageway roads, the average free flow speed is below the designated speed limit for each vehicle type, except motorcycles on motorways.[29]