A little bit of history which may be of interest - from Wikipedia ( that irrefutable source )
1945–1969[edit]
On 1 October 1956, the 30 mph (48 km/h) speed limit for built-up areas became permanent under the Road Traffic Act 1956. The speed limit, introduced on a trial basis in 1935, had relied on being renewed by Parliament each year.[50] The maximum speed limit for goods vehicles was raised from 20 mph (32 km/h) to 30 mph (48 km/h) in 1957.[51]
Following a series of serious motorway multiple crashes in the fog in 1965, Tom Fraser, the then Minister of Transport, following consultations in early November with the police and with the National Road Safety Advisory Council (NRSAC), concluded that the crashes were caused by vehicles travelling too fast for the prevailing conditions. The NRSAC advised that a 20 mph (32 km/h) motorway speed limit should be imposed on motorway stretches affected by fog and that a general speed limit of 70 mph (113 km/h) should be experimentally applied for the winter months.[52]
On 25 November 1965 the government announced that a temporary 30 mph (48 km/h) speed limit would be applied to sections of motorway (there were 350 miles (560 km) of it at that time) affected by fog, ice or snow and that a general maximum speed limit of 70 mph (113 km/h) would be applied to all otherwise unrestricted roads, including motorways, for a trial period of four months starting just before Christmas.[11] The four-month trial 70 mph (113 km/h) speed limit on 100,000 miles (160,000 km) of previously unrestricted roads and motorways was introduced at noon on 22 December 1965.[53] Also on that day, the power for the police to apply advisory speed limits of 30 mph (48 km/h) to motorways affected by bad weather was also introduced. The advisory limit was activated by the use of flashing amber lights placed at 1 mile (1.6 km) intervals along the motorways.[53]
In April 1966 Barbara Castle, the new Minister of Transport, decided to extend the experimental 70 mph (113 km/h) limit for a further two months to allow the Road Research Laboratory (RRL) time to collect data as there was still no conclusive evidence of its effectiveness.[54] In May 1966 Barbara Castle extended the experimental period by a further fifteen months to 3 September 1967 as "the case is not proven" but there were signs of crash rate reduction.[55]
In July 1966 the speed limit for "public service vehicles" (notably buses) was raised from 40 mph (64 km/h) to 50 mph (80 km/h).[56] During 1966, the highest number of fatalities during peacetime at 7,985 deaths, was recorded.[n 8]
In July 1967, Castle announced that 70 mph (113 km/h) was to become the permanent maximum speed limit for all roads and motorways. She had accepted RRL evidence that the speed limit had reduced the number of casualties on motorways. She ruled out minimum speed limits for motorways which would also reduce the danger of slow traffic as being too difficult to enforce and likely to increase congestion off the motorways.
The two major motoring organisations at the time, The Automobile Association and the R.A.C. welcomed the maximum speed limits for all-purpose roads, but the R.A.C. would have preferred more flexibility for motorways. The Royal Society for the Prevention of Accidents suggested that a lower speed limit would be more appropriate for all-purpose roads and the Pedestrian's Association for Road Safety condemned the new limits as being too high, preferring 60 mph (97 km/h) limits for all roads.[57] Castle's decision and acceptance of the RRL research at face value was controversial. Peter Walker's motion in Parliament to annul the speed limit on motorways was negatived.[58]
1973 oil crisis[edit]
Due to the 1973 oil crisis, a temporary maximum national speed limit of 50 mph (80 km/h) for all roads, including motorways, was introduced on 8 December 1973.[16] The 70 mph (113 km/h) limit was restored on motorways in March 1974 and on all other roads on 8 May 1974.[59]
As an initiative to reduce energy consumption, the national speed limits for otherwise unrestricted single-carriageway and dual-carriageway roads were temporarily reduced to 50 mph (80 km/h) and 60 mph (97 km/h) respectively (motorway speed limits were left unchanged at 70 mph (113 km/h)) from 14 December 1974.[60] In November 1976 the temporary speed limits were extended at least until the end of May 1977.[61] In April 1977, the government announced that the national speed limits for single-carriageway roads was to be increased to 60 mph (97 km/h) and that the 70 mph (113 km/h) speed limit was to be restored on dual-carriageways on 1 June 1977.[62][63]
1977–present[edit]
A speed limiter requirement for mopeds was introduced in 1977, with the speed cap being progressively redefined from 35 mph (56 km/h), to 30 mph (48 km/h), back up to 50 km/h (31 mph) and finally to 45 km/h (28 mph) in the late 2000s.[n 2]
The 70 mph (113 km/h) speed limit was made permanent in 1978.[n 11]
The Road Traffic Regulation Act, which was passed in 1984, includes legislation relating to speed limits. Part VI of the Act[64] defines the default speed limit for 'regularly'-lit roads,[65] gives local authorities powers to create 'speed limit orders', and exempts emergency vehicles from speed limits; the Act also defines speeding offences.[66]
The first 20 mph (32 km/h) speed limits for residential areas were introduced in 1991[n 12] and then speed limiters for buses and coaches set at 65 mph (105 km/h) and also for HGVs set at 56 mph (90 km/h) in 1994.[n 1] It was made easier for local authorities to introduce a 20 mph (32 km/h) limit in 1999.[67]
In March 2009 the government consulted on reducing speed limits on rural roads on which 52% of fatalities had occurred in the previous year to 50 mph. They explained that 'crashes were more likely on rural parts of the road network, upon most of which the national speed limit of 60 mph applies'. The Conservative opposition party and the AA were both opposed. The president of the AA said that speed limits that are too low can result in a greater number of accidents and that a "blanket reduction of speed limits would not make roads safer, given that many accidents on rural roads involved only one car".[68]
In February 2010 the Department for Transport proposed that the speed limit for all road vehicles able to carry more than 8 people should be set at 65 mph.[69]
In April 2015 the speed limit for Heavy Goods Vehicles over 7.5t was increased on dual carriage ways from 50mph to 60mph.[70]