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{{Term Box | name = Smart Motorway | galleryname= | image = Early Morning Traffic on the M42 Motorway - Geograph - 86205.jpg | caption = Variable speed limits in use on the M42 | quick = [[Ramp Metering]]{{-}}[[Motorway]] | terms = Active Traffic Management{{-}}Managed Motorway }} Smart Motorways (formerly known as Active Traffic Management (ATM) and Managed Motorways) are sections of motorway that use additional technology to manage traffic flow.

Smart motorways are equipped with variable speed limits and, depending on the needs of each individual scheme, may also include hard shoulder running (the use of the hard shoulder as an additional lane) and ramp metering. Hard shoulder running (the use of the hard shoulder as an additional lane) can take two forms: dynamic hard shoulder or all lane running (see below: how it works). Where additional capacity is required on the mainline through junctions, changes to junctions may take place to accommodate this.

Electronic signs and signals play a major role on smart motorways, and the most advanced equipment is used. Emergency areas are provided to provide a place of relative safety when the hard shoulder is not available - these are akin to laybys, but may only be used in an emergency.

Key operational principles

The objective of smart motorways is to increase motorway capacity, and optimize the use of this capacity, without requiring lengthy and expensive carriageway widening. Technology-driven approaches are used to help manage traffic flow, and keep travelers updated with real-time traffic information.

Smart motorways are always equipped with variable mandatory speed limits, which are displayed in a red circle and are enforced by variable HADECS3 cameras. Traffic levels are continuously monitored, through loops in the road on older schemes, and through radar on newer schemes. Pan-tilt-zoom CCTV cameras are available too, allowing operators in the National Highways Regional Control Centres to monitor any part of the motorway.

Congestion management and queue protection

When traffic levels build up, variable speed limits are brought in automatically by the advanced queue protection systems. This can also be done manually by operators in the Regional Control Centres. Sometimes this by itself may be enough to prevent the onset of congestion, and can be supplemented by ramp metering where this is available. On dynamic hard shoulder schemes, the hard shoulder will remain closed in the first instance, though operators in the Regional Control Centre in charge of the scheme may prepare to open it if further congestion is predicted. Overhead MS4 message boards may encourage drivers to avoid changing lane:

Congestion stay in lane

If congestion is still building up, on schemes with a dynamic hard shoulder, operators at the Regional Control Centre in charge of the scheme will be advised that extra capacity is needed. They will then prepare 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, this is done using cameras that are placed at increased frequency along the hard shoulder. If the hard shoulder is clear, the red X above it will change to a speed limit to indicate that it is open to all traffic. Overhead MS4 message boards will display a verbal message to supplement this:

Use hard shoulder

If the cause of congestion is identified to be traffic backing up from the next junction, the hard shoulder can be designated as an extended slip road (as opposed to a general running lane), and overhead MS4 message boards will instruct traffic planning to exit to move into the hard shoulder. Where the junction concerned is an interchange between motorways, the MS4 message boards may show the number of the motorway instead of the junction number.

Use hard shoulder for [J11] only (at junctions with the local road network)
Use hard shoulder for [M5] only (at interchanges between motorways)

(note that the numbers in brackets would vary based on the specific location)

If an obstruction is detected, the sequence is aborted, the hard shoulder remains closed, and National Highways will deal with the obstruction (for example, providing assistance to a broken down vehicle).

On controlled and all lane running motorways, the hard shoulder opening sequence does not apply, as the fourth lane is available at all times. The objective is that the fourth lane will delay or prevent the formation of queues. Variable speed limits and the message "Congestion stay in lane" are then used if any further traffic management is necessary.

Incident management

During an incident, the Smart Motorway system can be used to show informational and warning messages, and set speed restrictions, lane closures, and, in extreme cases, closures of the entire motorway.

Comparison to conventional motorways


Feature	Smart motorways	Conventional motorways
Number of lanes	Normally four lanes, but sometimes three, and occasionally more than four (e.g. M25 and M4 near Heathrow Airport). May also be supplemented by a dynamic hard shoulder.	Two, three, or four lanes - rarely more than four. Most motorways that have been recently upgraded with four or more lanes have been equipped with smart technology.
Hard shoulder	This depends on the type of smart motorway. Controlled motorway: permanent hard shoulder for emergency use only. May be discontinuous under bridges or over underpasses. Dynamic hard shoulder: hard shoulder defaults to emergency use only, but can be opened as a traffic lane as and when extra capacity is required. All lane running: mostly no hard shoulder. However, hard shoulders may still be provided on slip roads, through junctions which have not been equipped with through-junction running, or in other specific circumstances (e.g. where there was previously a discontinuous fourth climbing lane).	Permanent hard shoulder for emergency use only. May be discontinuous under bridges or over underpasses.
Emergency areas	Where the hard shoulder is being temporarily used as, or has been permanently converted to a running lane, emergency areas are provided as a place of relative safety. National Highways emphasizes that unlike lay-bys, these are for emergency use only. They contain emergency roadside telephones, and drivers are required to use the telephone to alert National Highways of their presence and obtain safety advice before attempting to rejoin the carriageway.	Not needed due to the presence of a full-time hard shoulder, but very rarely, a few do exist.
Variable speed limits	Always mandatory, and shown within a red circle on variable message signs. Enforced using HADECS3 cameras mounted to the side of the gantries (previously HADECS2 cameras, a design based on the Gatso, mounted behind each AMI lane control signal).	Advisory limits only - shown without a red circle (but sometimes with amber flashing lights) on variable message signs. The national speed limit remains the legally enforced limit at all times.
Variable signs and signals	This depends on the type of smart motorway. Controlled motorway: gantries, each with AMI lane control signals and either a 2x12 EMS or MS4 message sign Dynamic hard shoulder: gantries, each with AMI lane control signals and an MS4 message sign All lane running: a single gantry with AMI lane control signals and an MS4 message sign is provided after each junction and periodically on long stretches between junctions. Apart from this, MS4 message signs are mounted individually in the verge, but these are capable of showing speed limits and lane control simultaneously, unlike their counterparts on conventional motorways.	This will often depend on how busy the stretch in question is - however there are some anomalies of motorways that have been over- or underspecified. Quiet stretches of rural motorway may only have MS1 signals in the central reservation every two miles. Rural stretches of more major motorways often have MS3 or MS4 signs mounted individually in the verge every mile, capable of providing advisory speed limits or lane closures alongside a message and, on MS4 signs, a warning legend. On stretches with four or more lanes, when approaching major interchanges, in and around major cities, or which are otherwise very busy, lane control signals are fitted - see below.
Lane control	Comprehensive lane control provided - either through AMI (Advanced Motorway Indicator) lane control signals, or using lane control diagrams on verge-mounted MS4 signs. Lane diversions and closures always accompanied with mandatory reduced speed limit - to help ensure vehicles move through safely. Lane closures using Red X legends - both on lane control gantries and verge mounted signs. These are mandatory, and enforced automatically by HADECS3 cameras.	Comprehensive lane control is not often provided. Gantries with MS1 lane control signals (and in a few rare cases, AMIs) are usually only installed on stretches with four or more lanes, when approaching major interchanges, in and around major cities, or which are otherwise very busy. Where lane control is provided, lane diversion and closure symbols are accompanied with advisory speed limits, but neither lane diversions nor Lane closures using Red X legends are only provided in areas equipped with MS1 lane control. The Red X is mandatory, but unlike smart motorways, automatic enforcement cameras are not normally installed. Where lane control gantries are not installed, "wicket" legends are used to warn of closed lanes on variable signs and signals. These do not have the same effectiveness as the Red X as they are only advisory - and cannot be accompanied by reduced speed limits,

History and development

Variable Speed Limits and Ramp Metering have been trialed as individual solutions before - the former first appearing on the M25's south-western quadrant in 1995 - but smart motorways involve the concurrent use of multiple traffic management measures, tailored to the needs of individual schemes.

M42 Active Traffic Management pilot

The first smart motorway scheme was launched in 2006, on the M42 between junctions 3A and 7. The scheme, branded Active Traffic Management (ATM) at the time, involved Variable Speed Limits, Ramp Metering, and a dynamic hard shoulder. Additional strategies, such as variable HOV/HGV lanes, peak-time overtaking bans, variable road markings, and more, were considered too, but were never implemented.^[1] As the pilot scheme, the M42 was given bespoke new signage, indicating the start of active traffic management, and warning of variable speed limits ahead. This signage remains on the M42 today, though it cannot be seen elsewhere; all future schemes were equipped with simpler signage of a different design.

Further rollout of dynamic hard shoulder schemes

The M42 pilot scheme showed mainly positive results, and so plans to introduce similar technology to much of the English motorway network, now under the name Managed Motorways, were announced by the Department for Transport in early 2009, and shortly afterwards a scheme was introduced on the M6, also near Birmingham.

Over the next few years, until around 2012, most new smart motorways took a similar form. The M42 and M6 schemes were extended, and sections of the M1, M4, and M5 received variable speed limits and dynamic hard shoulders. However, these new schemes were slightly watered down to reduce costs. The number of emergency areas was reduced, with the spacing between them increased. The design of through-junction running was changed, with a permanent fourth lane between junction slip roads.

Meanwhile, some other motorways, that were already in the process of being fully widened to D4M standard, opened as controlled motorways with variable speed limits (retaining a full-time hard shoulder), and many full widening schemes that were still in the design stage were considered for conversion to managed motorways instead.

Introduction of all lane running schemes

In 2011-2012, design options were being worked up to provide extra capacity to the M25 between junctions 23 (A1(M)) and 27 (M11). Though standard procedure at the time was to install dynamic hard shoulders, it was recognized that on this stretch, the extra capacity was in such high demand that hard shoulder running would likely have been necessary for most or all of the day.

As a result, a new configuration was created, known as all lane running, where the hard shoulder is permanently converted into a running lane, to avoid the need for excessive use of electronic signalling.

All lane running schemes, including the two used on the M25, still include variable speed limits and lane control, but there is no visible hard shoulder at all.

In 2019, a stocktake on the safety of smart motorways was ordered by Transport Secretary Grant Shapps^[2], with the

It is the preferred option for increasing motorway capacity, as it is much more ecnomically viable than full widening of motorways to D4M standard, which can cost more than £30m per mile widened. However, many concernshave 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. {{Agency|England}} explains this is to reduce confusion as to if the hard shoulder is open or not. [1]. 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. [2]

Safety concerns

List of schemes

Current Smart Motorways

Key: DHS: Dynamic Hard Shoulders, ALR: All Lanes Running, VSL: Variable Speed Limits, MTR: Ramp Metering, TJR: Through Junction Running

Image

Road

Junctions

Elements

Installed

Notes

File:M1 widening J9 - Coppermine - 18695.jpg

{{J|M1|6A}} - {{J|M1|10}}

VSL

Equipment already installed in 2008 widening.

File:M1, southbound - Geograph - 4730118.jpg

{{J|M1|10}} - {{J|M1|13}}

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.

{{J|M1|28}} - {{J|M1|31}}

ALR, VSL

March 2016

{{J|M1|31}} - {{J|M1|32}}

VSL

March 2016

{{J|M1|32}} - {{J|M1|35A}}

ALR, VSL

J34 - 35A opened to traffic in December 2016, J32-34 is still under construction.
Lane drop through J24.

{{J|M1|39}} - {{J|M1|42}}

ALR, VSL

December 2015

{{J|M4|19}} - {{J|M4|20}}

DHS, VSL

Spring 2014

In conjunction with M5 J15 - 17

{{J|M5|15}} - {{J|M5|17}}

DHS, VSL

Spring 2014

In conjunction with M4 J19 - 20

{{J|M6|4}} - {{J|M6|5}}

DHS, VSL, MTR, TJR (J4A west only)

November 2009

{{J|M6|5}} - {{J|M6|8}}

DHS, VSL, TJR

Spring 2013

Strengthening of the hard shoulder took place Between September 2009 and March 2010. Highways Agency Project

File:M6 ATM- Geograph - 1680317.jpg

{{J|M6|8}} - {{J|M6|10A}}

DHS, VSL, MTR

{{J|M6|10A}} - {{J|M6|11A}}

VSL

February 2016

{{J|M6|11A}} - {{J|M6|13}}

ALR, VSL

February 2016

{{J|M23|8}} - {{J|M23|10}}

ALR, VSL

Summer 2020

Spur

{{J|M23|9}} - {{J|M23|9A}}

ALR (Airport-bound ONLY)

Winter 2019

fixed 50MPH speed limit

{{J|M25|5}} - {{J|M25|7}}

ALR, VSL

Spring 2014

{{J|M25|23}} - {{J|M25|27}}

ALR, VSL

November 2014

File:M42 Motorway North or West at Junction 3a - Geograph - 1283022.jpg

{{J|M40|16}} - {{J|M42|3A|showroad=true}}

VSL (Westbound only)

2009

{{J|M42|3}} - {{J|M42|3A}}

VSL (Eastbound only)

2009

File:M42 TJR VMS.JPG

{{J|M42|3A}} - {{J|M42|7}}

DHS, VSL, MTR, TJR (J5 south only)

September 2006

The original trial instalation, publicly branded as "Active Traffic Management"

{{J|M42|7}} - {{J|M42|9}}

VSL

2009

{{J|M62|25}} - {{J|M62|26}}

ALR, VSL

September 2013

{{J|M62|26}} - {{J|M62|30}}

DHS, VSL

September 2013

Schemes under construction

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	J7 - J10
M25	J23 - J27		Spring 2013	Autumn 2014
M60	J8 - J18	VSL	July 2014	September 2017		{{Agency\|England}}
M62	J18 - J20	ALR, VSL	July 2014	September 2017		{{Agency\|England}}
M62	J25 - J30