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What is a smart motorway?

Ellie Dyer-Brown, 1 year ago

3 min read

  • Advice
  • what

WhoCanFixMyCar explains what smart motorways are and how they affect drivers

Smart motorways are undoubtedly a hot topic at the moment - and a controversial one, too. Like them or loathe them, it pays to be aware of how they operate and how they differ from conventional motorways because, despite the government pausing their rollout in lieu of conclusive safety data, a number of them have already been built across the country.


What is a smart motorway?

How do smart motorways prevent traffic bunching?

Smart motorway signs

Where are smart motorways UK?

Are smart motorways dangerous?

What is a smart motorway?

Smart motorways are designed to be extremely efficient owing to the traffic management methods they use to reduce congestion and increase capacity. 

Usually, this involves using the hard shoulder as a regular lane and implementing variable speed limits.

Smart motorways were designed by Highways England to manage traffic while crucially minimising environmental impact. However, as we’ll discuss later on in this article, they have certainly come under fire thanks to safety concerns.

There are three main types of smart motorway:

  • ‘All lane running’ schemes 

  • ‘Dynamic hard shoulder’ schemes

  • ‘Controlled motorway’ schemes

‘All lane running’ smart motorway schemes

In ‘all lane running’ schemes, there is no longer a hard shoulder; instead, there is an extra lane that will only be closed to traffic if there is an accident.

If an accident does happen, one or more lanes could end up being closed. This is always signalled by a red X that will appear on an overhead gantry or a sign at the edge of the road. When you see a red X, exit that lane as soon as you can; failing to do so is not only dangerous but illegal.

Signs are also used to show the speed limit which varies depending on the level of traffic. 

‘Dynamic hard shoulder’ schemes

During the busiest parts of the day, the hard shoulder is opened up to ease congestion, and this is indicated by overhead signs.

Again, overhead signs display the speed limit which varies depending on the volume of traffic. 

‘Controlled motorway’ schemes

Controlled motorways still have a traditional hard shoulder with three lanes or more. However, these lanes are subject to a variable speed limit which is displayed by overhead signs. The national speed limit applies if a speed limit is not indicated above.

How do smart motorways prevent traffic bunching?

Smart motorways prevent long queues and congestion by using variable speed limits. Some of them also control the traffic flow by opening up the hard shoulder as a regular lane.

Smart motorway signs

On smart motorways, a red X always signals that a lane is closed and should not be used. 

Sometimes, red X signs need to be implemented in advance of an incident to provide access for emergency vehicles, so even if you can’t see why a lane is closed, it’s important that you don’t use it. 

Where are smart motorways UK?

There are over 236 miles of smart motorway in the UK.

M1 - Junctions:16-19, 24-25, 28-31, 32-35a, 39-42, 10-13, 6a-10, 23a-24, 25-28, 31-32

M3 - Junctions: 2-4a

M4 - Junctions: 4-5 interchange

M5 - Junctions: 4a-6

M6 - Junctions: 2-4, 11a-13, 16-19, 4-5, 5-8, 8-10a, 10a-11a

M20 - Junctions: 3-5, 5-7

M23 - Junctions: 8-10

M25 - Junctions: 5-7, 23-27, 2-3, 7-10, 10-16, 16-23, 27-30

M42 - Junctions: 3a-7, 7-9

M60 - Junctions: 8-18

M62 - Junctions: 18-20, 10-12, 25-30

Are smart motorways dangerous?

Although early data shows that they have head a positive impact, there are a number of valid concerns about smart motorways. Some drivers have expressed worry about road safety thanks to the variable speed limits which could require them to slam on their brakes to slow down in time. 

In response, Highways England has clarified that there is a slight lag between when the speed limit is changed and when cameras start enforcing the new limit. However, this can be as little as ten seconds, which fails to reassure many motorists.

Additionally, data collected since the first smart motorway opened in 2006 suggests that journey reliability has improved by 22% and personal injury accidents have been reduced by more than half. 

That being said, many people feel that motorways without a permanent hard shoulder are unsafe; the crime commissioner for South Yorkshire has been a vocal opponent, and a YouGov poll in 2021 found that the majority of motorists agree. 

Despite the seemingly positive smart motorway data from Highways England, the government has made the decision to pause rolling out the smart motorway network for the next five years. During this time, £900 million is also being invested in improving existing smart motorways to ensure people feel safer.

This will come as welcome news to motorists who believe that some of the existing smart motorways have been built without enough safety laybys or cameras for when breakdowns occur.

Currently, the furthest distance between emergency laybys is 1.5 miles, which, in the eyes of many, is simply too far to be safe.

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