Smart motorway

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).

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 60 miles per hour (97 km/h) was trialled 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 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 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. 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.