Smart motorways: What are smart motorways, where are they in the UK and why are drivers being fined for using them?

Parts of the M3 in Hampshire have been undergoing upgrades for what feels like years, with speed restrictions, average speed cameras and narrow lanes causing traffic chaos. These upgrades include turning the “dumb” motorway into a smart one; to add technical features seen on other parts of the M3 as well as other smart motorways across the UK.

Now, drivers on the M23 are set to face similar delays and disruption with parts of the road around Gatwick Airport being widened ahead of it being turned into a smart motorway. The work will be carried out between junction 8 at Merstham and junction 10 at Copthorne.

While it may seem like a recent term, smart motorways aren’t that new, it’s just that the definition and functions of smart motorways are changing and will likely add many more features in the future – some of which are controversial. In a recent The Times report, figures from Highways England revealed 72,348 people have been fined on so-called smart motorways with variable speed limits in the past year. This was almost double the number seen in the previous year, and represents a tenfold increase in five years.

In particular, two thirds of these fines were given to motorists travelling slower than 70mph because of the temporary speed limits imposed by smart motorway signage. Smart motorways use data to predict when congestion will build and the signs will often drop the speed limit in anticipation of such traffic. However, often the congestion doesn’t materialise or the traffic management schemes work so well, they help manage traffic in a way that means drivers are forced to travel at restricted speeds on empty motorways. 

If these drivers then speed up to the national speed limit, while the smart motorway signs show 40mph or 50mph, they can be fined. Highways England has insisted it is providing training so its staff can remove “inappropriate” lower speed limits when needed, but the AA voiced concerned that thousands of drivers could have been wrongly fined.

Read on to learn more about smart motorways and where are smart motorways in the UK?

Smart motorways: What are smart motorways?

 Smart motorways, once referred to as managed motorways, were first introduced in 2006 on the M42 in the West Midlands. They’re defined as stretches of motorway that use so-called active traffic management (ATM).

These speed and lane techniques are designed to control the flow of cars, to avoid bottlenecks and traffic congestions, as well as increase capacity of the road by opening the hard shoulder at busy times. They’re controlled using signs on gantries and monitored using cameras and sensors.

According to the Highways Agency: “By varying speed limits and using the hard shoulder as an extra lane during busy times, we can help you to avoid having to brake or be at a standstill so that you get to where you need to be on time.”

Smart motorways differ slightly from “controlled motorways”, which typically adopt the variable speed limits seen on the smart motorways but without the hard shoulder features.

How do smart motorways work?

Sensors fitted onto the road, as well cameras on gantries, are used by the agency to monitor traffic and congestion. These can also be used by law enforcement agencies.

These monitoring sensors activate lower speed limits, or limits can be applied remotely by people monitoring for accidents and other incidents.

Types of smart motorways

There are four types of smart motorway:

Controlled motorways: Variable speed limits without the hard shoulder. Controlled motorways typically have three or more lanes and on controlled motorways, the hard shoulder should only be used for breakdowns or genuine emergencies.

Dynamic hard shoulder: Variable speed limits with the hard shoulder being used at select times to reduce congestion. A white line is used to distinguish between the standard lanes and the hard shoulder and signs above lanes on gantries show which lanes are in operations. When a lane is closed, a red X will appear above the restricted lane. Driving under a red X sign is illegal. These signs also show any restricted speed limits being enforced.

All lane running: Variable speed limits with the hard shoulder being turned into a permanent lane. This scheme is similar to the dynamic hard shoulder scheme and uses gantry signs to show speed limits and lane closures.

Through junction running: This was seen on older smart motorways and was used to describe when a hard shoulder could be used ahead of a junction. They are few and far between in the UK now. 

Smart motorways map


This map shows the location of smart motorways in the UK as of 2017

Smart motorway cameras and how to use a smart motorway

The official guidance from the Highways Agency states that speed limits displayed in a red ring are mandatory and must be followed. When no speed limit is shown, the national speed limit of 70mph is in place. Variable mandatory speed limits displayed in a red circle mean it is the law to follow the speed limit.

This video explains more:

YouTube video

While many motorists believe smart motorway speed cameras are only active when a variable speed limit has been put in place (when the variable speed limit is shown on gantry signs), a recent FOI request found that cameras on the M1, for example, can catch drivers breaking the 70mph limit as well as those breaking lower, variable limits.

The four cameras on that stretch of road caught 8,382 speeding drivers in 2017, making them the most profitable cameras in the county in 2017.

The future of smart motorways

The reason smart motorways have made headlines recently are the upgrades and proposals being made to the existing, somewhat basic systems.

Highways England is planning to fit miles of fibre optic cables that will run along busy motorways between London, Bristol, Leeds and Manchester that will use superfast 5G broadband to beam traffic information straight to phones.

This information will include details about road diversions, heavy traffic, and will advise motorists to change lanes if there’s been an accident. The agency even claims its fibre network will be able to “anticipate” heavy traffic on roads and give alternative routes to motorists in real time and with plenty of notice. 

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Highways England has also proposed using drones to alert the National Roads Telecommunications Service about congestion, while connected vehicles will be able to alert Highways England of potholes. 

Elsewhere, the agency has begun rolling out smart LED road studs – commonly known as cat’s eyes – at at Switch Island junction in Merseyside. This is one of the country’s busiest junctions, where the M57, M58 and a trio of A roads meet.

It is used by around 90,000 vehicles each day, and is currently undergoing a £3 million safety initiative as an average of one accident happens on it every fortnight.

The smart studs are synchronised with nearby traffic lights linked by a series of underground wires. They turn off when the lights go red.

The intelligent cat’s eyes have already been installed in the Hindhead Tunnel in Surrey, but this latest scheme will be the first time they have been linked to traffic lights at a motorway junction.

Where are smart motorways in the UK?

The list of currently operational smart motorways in number order is shown below alongside their relevant schemes.


J6a-J10: Controlled motorway (CM)

J10-J13: Dynamic hard shoulder (DHS)

J16-J19: All lane running (ALR)

J25-J28: CM

J28-J31: ALR

J31-J32: CM

J32-J35a: ALR

J39-J42: ALR


J2-J4a: ALR


J19-J20: DHS

J24-J28: CM


J4a-J6: ALR

J15-J17: DHS


J4-J10a: DHS

J10: Through junction running

J10a-J11a: CM

J11a-J13: ALR


J4/J5-J7: CM


J20-J3: CM

J5-J6: ALR

J6-J7 anti-clockwise: CM

J6-J7 clockwise: CM

J7-J23: CM

J23-J27: ALR

J27-J30: CM


J3a-J7: DHS


J3a-J7: DHS

J7-J9: CM


J18-J20: ALR

J25-J26: ALR

J26-J28: DHS

J28-J29: CM

J29-J30 east: DHS

J29-J30 west: ALR


J1a-J3: DHS

Image: Shutterstock/Keith Michaels via Wikimedia Commons

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