A smart motorway (formerly managed motorway) is a section of motorway in Great Britain that uses active traffic management (ATM) techniques to increase capacity by use of variable speed limits and hard shoulder running at busy times. Benefits include smoother traffic flow, more reliable journey times, fewer road traffic collisions, and reduced noise and harmful vehicle emissions. The term controlled motorway is used for schemes that use variable speed limits without hard-shoulder running (for example, the M25 from J27 to J30).
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History
The technique was first used in the UK on the M42 motorway in the West Midlands in 2006. A higher speed limit of 60 miles per hour (97 km/h) was trialed on the southbound carriageway between junctions 4 and 3A from 2008 (a 10 miles per hour (16 km/h) increase on the previous maximum permissible speed).
In 2007 plans were announced to extend the scheme to two sections of the M6 near Birmingham (4-5 and 8a-10) by 2011 for £150 million. The emergency refuges were to be extended to every 800 metres (0.50 mi) 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. In March 2012 the government indicated that was considering a trial of higher 80 mph speed limit on some Managed Motorways although proposals for higher speeds on motorways were met with caution on a number of grounds by both motoring and road safety organisations.
Operation
Highways England (formerly known as the Highways Agency), Transport NI, Transport Scotland (who promote the technology as Intelligent Transport Systems) and Traffic Wales are responsible for the schemes in England, Northern Ireland, Scotland and Wales respectively. In the following table, schemes are classified into 3 types:
As of April 2016 the following schemes are operational, under construction or planned:
Effectiveness
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.
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 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 minute 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.
Criticisms
The Campaign for Better Transport argued that whilst it would reduce the need for widening schemes, it did nothing to reduce traffic and CO2 emissions. Friends of the Earth criticised the scheme as "widening on the cheap" and also pointed to a possible increase in vehicle emissions. Highways England argue that ATM reduces the environmental impact in regards to widening as it is carried out within the existing boundaries of the motorway as well as a possible improvement in local air quality due to smoother traffic flow.
The RAC cited a study in the Netherlands that showed drivers using the hard shoulder when they were not permitted, increasing the risk of a collision for vehicles stopped. The Royal Society for the Prevention of Accidents also expressed concern that emergency services would take longer to reach an incident. The Highways Agency rejected this concern based on the 5,000 miles of dual carriageway that does not have a hard shoulder. Disability groups were concerned that some drivers would not be able to access the emergency phones or even exit their vehicles, leaving them at increased risk. Ruth Kelly, former Secretary of State for Transport stated that these schemes were useful, but that motorway widening would still be considered where it was appropriate.