Smart motorway

A smart motorway (formerly managed motorway and active traffic management), also known in Scotland as an intelligent transport system, is a section of motorway in the United Kingdom (primarily in England) that employs active traffic management (ATM) techniques to increase capacity through the use of MIDAS technology including variable speed limits and occasionally hard shoulder running and ramp metering at busy times. They were developed at the turn of the 21st century as a cost-effective alternative to traditional carriageway widening, with intended benefits ranging from more reliable journey times to lower vehicle emissions.^[1][2][3] However, despite the risk of a collision occurring between two moving vehicles being found to be decreased, there has been an acknowledged rise in the incidence of collisions involving vehicles where at least one was stationary in the first few years following the widespread removal of the hard shoulder on the country's busiest sections of motorway.^[4] Smart motorways garnered intense criticism from politicians, police representatives and motoring organisations, particularly from 2020 onwards, after a surge in near miss incidents and dozens of fatalities were revealed,^[5][6] and as of April 2023, no new smart motorways will be built.^[7]

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).