A smart motorway (formerly managed motorway), also known in Scotland as an intelligent transport system, is a section of motorway in the United Kingdom that employs active traffic management (ATM) to increase capacity. Technologies used include Motorway Incident Detection and Automatic Signalling (MIDAS), variable speed limits and variable lane control. At particularly busy times, ramp metering may be used, and some roads permit the hard shoulder to be used as a running lane.
Smart motorways were developed at the turn of the 21st century as a cost-effective alternative to traditional carriageway widening, with intended benefits ranging from shorter journey times to lower vehicle emissions. However, smart motorways have received intense criticism from politicians, police representatives and motoring organisations, mainly for perceived reductions in safety, particularly regarding the removal of the hard shoulder from some sections of motorway. Such roads are known as all-lane running (ALR) motorways, and replace the traditional hard shoulder with a full-time running lane with discrete emergency refuge areas. A 2020 government report found that ALR conversions reduced the frequency of fatal casualties, but increased the frequency of non-fatal casualties. The incidence of collisions between moving vehicles decreased, but collisions between moving and stationary vehicles increased.
In April 2023, the government scrapped plans for the building of all new smart motorways, citing costs and a "lack of confidence felt by drivers" as reasons for the decision.
The term controlled motorway is sometimes used for schemes that use variable speed limits without hard-shoulder running (for example, the M25 motorway between junction 27 and junction 30).
History The traffic management technique, including hard shoulder running, was first used in its full specification in the UK on the M42 motorway in the West Midlands in 2006. A higher speed limit of was trialled on the southbound carriageway between junctions 4 and 3A from 2008 (a increase on the previous maximum permissible speed).
In 2007 plans were announced by the then secretary of state for transport, Ruth Kelly, to extend the scheme to two sections of the M6 motorway near Birmingham (4-5 and 8a-10) by 2011 at a cost of £150 million. The emergency refuges were to be extended to every on the roll out. A study into the use of ATM on the M1, M4, M20 and M25 motorways was also announced, however the Department for Transport had decided to proceed with a scheme to widen sections of the M25.
A £2 billion contract was announced to extend the scheme to sections of the M1, M4, M5, M6, M60 and M62 in February 2010 with a further announcement by the new government in October 2010. The contract was awarded to four delivery partners Balfour Beatty, Carillion and joint ventures BAM Nuttall/Morgan Sindall and Costain Group/Serco. In January 2012, Carillion won the contract for M6 junctions 5 - 8 near Birmingham for £126 million.
From 2013 the current term smart motorway was used by the Highways Agency (now National Highways) to promote the technology to road users.
In January 2018, the contracts previously awarded to Carillion were taken on by Kier, following the former's entry into compulsory liquidation.
In April 2021, the government announced that new smart motorways would include radar, to detect vehicles which had stopped, and additional cameras to aid the detection (and subsequent prosecution) of motorists using lanes which are marked as being closed. The government stated that existing smart motorways would have these additional safety features installed by September 2022.
On 16 April 2023, the government announced that the smart motorways scheme would be halted permanently, citing "financial pressures and lack of confidence felt by drivers".
In June 2023, construction started to install over 150 additional emergency refuge areas on existing smart motorways as part of a national programme. This was completed in April 2025.
Features
Emergency refuge areas
In 2017, Highways England trialled a new type of emergency area on the M3 that would be more visibly obvious to motorists. A new sign accompanied the trial which is similar in design to European emergency area signs. These changes have subsequently been trialled on the M5 and M25 with the signs being authorised by the Department for Transport for further use.
Emergency stopping areas, when used correctly, are safer than hard shoulders. However, the government has subsequently reduced the specification of smart motorway design, increasing the minimum interval between refuge areas, possibly decreasing the likelihood of a driver being able to reach a place of relative safety in the event of a breakdown.
Stopped vehicle detection Some (18% in 2019) smart motorways employ stopped vehicle detection (SVD). The government states that all lane running motorways are designed to operate safely without the need for SVD, however SVD reduces the time it takes for National Highways control room staff to close the traffic lane to just one minute. < Text messages Early systems used dot matrix signs on gantries to display short text messages, with smaller variable signs above each lane and to the sides of the carriageway. Current smart motorway systems often use the "MS4" sign type which can include pictograms from the Traffic Signs Regulations and General Directions.
Variable lane control
To close a lane to traffic, the motorway gantries display a red cross (❌) to signify a lane closure. The red cross is a legal requirement for motorists under section 36(1) of the Road Traffic Act 1988 (failure to comply with a traffic sign), and failure to comply can result in a fixed penalty of £100 fine and three points. but can be penalised with a fine of up to £1,000 and a 56 day driving ban if prosecuted in court.
Compliance is at 92%, which has not decreased since 2019. Road users want to see a 'zero tolerance' approach towards vehicles disobeying a red cross.
Effectiveness
Reduced relative cost In 2007 it was estimated that ATM could be introduced within two years at a cost of around £5-15 million per mile as opposed to 10 years and £79 million per mile for widening.
In Autumn 2018, alteration of the M4 between junctions 3 and 12 was commenced, a length of 32 miles (51 km). Construction was completed in March 2022, but as of July 2022 calibration work of some sections is still underway. The cost was £848 million, representing £26.5 million per mile (£16.6 million per km). Emergency stopping areas in this section of the M4 have been provided every 1.3 miles (2.1 km).url=https://nationalhighways.co.uk/our-roads/south-east/m4-junctions-3-12-smart-motorway/
Initial experiments The M42 scheme was initially run as an experiment and a Highways Agency report into the first six months of the scheme showed a reduction in variability of journey times of up to 27%. The journey time statistics can be broken down to show that northbound journey times were reduced by 26%, equating to an average reduction of 4 minutes as compared to the period when the variable speed limits were on, but the hard shoulder was not being used, and 9% southbound (equating to 1 minute) during the afternoon rush hour. The report also indicated a fall in the number of accidents from over 5 a month to 1.5 per month on average. The Agency did state that normally accident statistics should be compared over a 3-year period, so the initial results should be treated with caution. They also stated that no accidents had been caused by hard shoulder use as a normal lane. The report also stated that there had been a 10% fall in pollution and 4% fall in fuel consumption. The report also indicated a compliance rate of 98% to the indicated speed limits when using the hard shoulder. For comparison, before the introduction of mandatory speed limits at road works, the compliance rate was 10% as opposed to 89% afterwards, showing a similar effect.
Road capacity All lane running motorway upgrades improve journey capacity. The Government argues that this improves safety as it encourages drivers away from statistically more dangerous rural or A roads. A smart motorway can carry 1,600 additional vehicles per hour in each direction, and up to 11,000 journeys a day.Written evidence submitted by the Department for Transport (RSM0113). committees.parliament.uk. Retrieved 8 May 2022.
In the short term, smart motorway upgrades can reduce journey times. For example, on the M6 around Crewe, the average commuting time decreased by an average of 40 minutes.
Public opinion A 2022 survey found that 73% of drivers will not use the leftmost lane on a smart motorway. This is an increase since 2019 (56%).
According to the RAC, only 23% of drivers trust that the highways authority can identify a stopped vehicle and respond accordingly'.
In 2022, 22% of drivers say they do not feel confident on motorways without a hard shoulder. This is compared to 12% on motorways with a hard shoulder and 8% on dual carriageways (normally without a hard shoulder).Smart motorways stocktake: Second year progress report 2022. National Highways, May 2022. Retrieved 22 May 2022.
Emergency refuge areas are currently provided up to 1.5 miles (2.5 km) apart. 63% of drivers believed this is too far and 79% of drivers are concerned they would not be able to reach a refuge in time.
Emergency vehicle access Due to the removal of the hard shoulder, there is some concern over the ability of emergency services and traffic patrol officers to access incidents on smart motorways when traffic is congested.
Safety Motorways are the safest roads in Great Britain, with more Killed or Seriously Injured (KSI) collisions recorded on A roads. Theoretically, smart motorways are designed to reduce certain types of risks through several features. For instance, traffic speeds tend to be more uniform, and technology is in place to monitor and notify drivers of potential hazards. Moreover, the emergency areas are intended to provide a safer place to stop compared to traditional hard shoulders.
Overall, Government statistics show that ALR smart motorways register well on safety performance. Statistics demonstrate a decrease in personal injury collision and casualty rates compared with the national trend. On individual conversions, a decrease in recorded after introduction of ALR. There was effectively no change in the Killed & Seriously Injured collision and casualty rates. However, Highways Magazine revealed that in the long-term, smart motorways may become more dangerous because the extra space they create is taken up by increased traffic.
All lane running (ALR) schemes - whereby the hard shoulder is removed - appear to be more unsafe because they design out the current principal safety mechanism on motorways - the hard shoulder. An independent review concluded that it is beyond doubt that the removal of a hard shoulder is less safe than any other form of 'smart' motorway.Independent Review of All Lane Running Motorways in England. Royal Haskoning DHV. Retrieved 8 May 2022.
All casualties According to a 2012 analysis by Highways England, ALR motorways were expected to lower risks by 20% when compared to conventional, three-lane motorways.Highways England and the Department for Transport monitored both slight and serious casualties between 2015 and 2018. The statistics revealed a small uptick in serious and slight casualties, but a slight decline in fatal casualties. However, accuracy is limited because road comparisons may not be entirely comparable. Per 100 million miles travelled, the following were measured –