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|Variable speed limits in use on the M42|
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|Ramp Metering • Motorway|
|Active Traffic Management • Managed Motorway|
Smart Motorways (formerly known as Active Traffic Management (ATM), Managed Motorways or Controlled Motorways) describes the modification of a motorway, usually in congested areas, with more advanced techniques to control and aid traffic flow. This either incorporates allowing traffic to drive on the hard shoulder under certain conditions (referred to as Dynamic Hard Shoulders or MM-DHS ) or converting the hard shoulder to a permanent traffic lane (referred to as All Lanes Running or MM-ALR). Originally referred to as Active Traffic Management, then Managed Motorways, latterly Highways England refer to these schemes as Smart Motorways.
On motorways upgraded to a Smart Motorway, more frequent overhead gantries or variable message displays are installed, emergency refuge areas (ERAs) are added to replace the loss of the hard shoulder, and variable speed limits are introduced. Signs and lights indicate if the hard shoulder is running and when to use it: sometimes the hard shoulder is used only for traffic heading off at the next junction, in other locations the hard shoulder might be converted to a running lane through the junction (known as Through Junction Running or TJR ).
The scheme is an expansion of existing schemes to use the motorway more effectively, such as Variable Speed Limits and Ramp Metering on motorways with variable traffic flows, where full widening might not be very cost-effective.
The first motorway to open with fully operating Active Traffic Management was the M42 between junctions 3A and 7. Plans to extend it to much of the English motorway network were announced by the Department for Transport in early 2009, and subsequently the scheme has been extended to the M6 and M40. It is an attractive political option because of its relatively low cost compared to full widening of motorways to D4M standard, which can cost more than £30m per mile widened. Concerns have been raised about the programme's safety implications as places to make emergency stops in the form of continuous hard shoulders are not available for much of the rush hour, as well as its longevity - the growth of traffic in the coming decades is likely to require more substantial widening or parallel construction at some point in the future.
Motorways being converted to Smart Motorways since 2013 will convert the hard shoulder to be a full-time running lane, as opposed to dynamic hard shoulders in previous schemes. Highways England explains this is to reduce confusion as to if the hard shoulder is open or not. . The new design standards include using MS4 full-matrix variable message signs mounted at the verge more frequently than overhead gantries, however signals over each lane will be provided at on-slips and periodically on a long stretch of All Lane Running motorway. The distance between the emergency refuge areas (laybys) are also extended to up to 2.5km. 
How it works
On motorways converted to Smart Motorway, cameras and traffic loops are built into the motorway. When the traffic levels build up, the Highways Agency Regional Control Centres (RCCs) will first try and ease congestion by bringing in Variable Speed Limits. Sometimes this by itself may be enough to prevent the onset of congestion. If this doesn't work, Ramp Metering may also be switched on, if available.
If congestion is still building up, on schemes with a Dynamic Hard Shoulder, the RCC prepares to activate the hard shoulder as a traffic lane. Before doing so, a careful sweep is made to ensure the lane is clear of broken-down vehicles or other obstructions. If the Hard Shoulder is clear, overhead message boards and variable signs change to indicate the lane is open to all traffic. (If an obstruction is detected, the sequence is aborted). In some cases, the hard shoulder is purely for traffic exiting at the next junction; at other times, it becomes a normal lane of the motorway.
When the hard shoulder is closed, either a red X (without the flashing lights) or a blank overhead sign appears above the lane. 
In an emergency, the gantry or overhead message signs are used to show which lanes are closed and to move traffic away from obstructions.
Current Smart Motorways
Key: DHS: Dynamic Hard Shoulders, ALR: All Lanes Running, VSL: Variable Speed Limits, MTR: Ramp Metering, TJR: Through Junction Running
|-||VSL||Equipment already installed in 2008 widening.|
|-||DHS, VSL||Dec 2012||Currently A5-M1 link roadworks going on - the ATM systems are partially inactive during this stretch. Construction due to end around 2018-2020.|
|-||ALR, VSL||March 2016|
|-||ALR, VSL|| J34 - 35A opened to traffic in December 2016, J32-34 is still under construction.
Lane drop through J24.
|-||ALR, VSL||December 2015|
|-||DHS, VSL||Spring 2014||In conjunction with M5 J15 - 17|
|-||DHS, VSL||Spring 2014||In conjunction with M4 J19 - 20|
|-||DHS, VSL, MTR, TJR (J4A west only)||November 2009|
|-||DHS, VSL, TJR||Spring 2013||Strengthening of the hard shoulder took place Between September 2009 and March 2010. Highways Agency Project|
|-||DHS, VSL, MTR|
|-||ALR, VSL||February 2016|
|-||ALR, VSL||Spring 2014|
|-||ALR, VSL||November 2014|
|-||VSL (Westbound only)||2009|
|-||VSL (Eastbound only)||2009|
|-||DHS, VSL, MTR, TJR (J5 south only)||September 2006||The original trial instalation, publicly branded as "Active Traffic Management"|
|-||ALR, VSL||September 2013|
|-||DHS, VSL||September 2013|
Future planned deployment
|Image||Road||Junctions||Elements||Expected Start||Expected Completion||Notes||Link|
|M1||J32 - J35A||2010/2011||2011/2012||Highways Agency|
|M3||J2 - J4A||November 2014||June 2017||Highways Agency|
|M5||J4A - J6||ALR, VSL||January 2016||November 2016||Highways Agency|
|M6||J13 - J19||DHS, VSL||After 2015||Strengthening of the hard shoulder took place Between September 2009 and March 2010||Highways Agency|
|M25||J5 - J7||Spring 2013||Summer 2014|
|M25||J7 - J10|
|M25||J23 - J27||Spring 2013||Autumn 2014|
|M60||J8 - J18||VSL||July 2014||September 2017||Highways England|
|M62||J18 - J20||ALR, VSL||July 2014||September 2017||Highways England|
|M62||J25 - J30|
The Highways Agency identified the following sections of motorway as having potential for future deployment of Smart Motorways - some sections have since been progressed to become schemes.
- The Highways Agency guide to Smart Motoways
- CBRD - Active Traffic Management
- Legislation - The Motorways Traffic (England and Wales) (Amendment) (England) Regulations 2015 - Legislation allowing for provision of Emergency Refuge Areas