Smart Motorways Explained

Smart motorways have become a fixture of British travel since their introduction in 2006 with the M42 trial.

A form of active traffic management system, the smart motorway is the more advanced cousin of the variable speed limit, which was introduced by the Highway Agency in 1995.

But what is a smart motorway? Well, let's get clever (or should that be smart?) and dispel the myths around the latest advancement in the UK’s motorway driving habits and traffic control systems.

What is a smart motorway?

Smart motorways are a motorway technology that checks and monitors road conditions and capacity to adapt to the situation to regulate the flow of traffic.

What's more, it’s believed that smart motorways should increase the ability of motorways to handle traffic by a third, but be more financially effective.

This traffic management system aims to prevent traffic bunching by controlling speed in sections, working for smoother, safer and more efficient journeys for all kinds of motorway users.

Using the overhead gantries and road signage, traffic flow can be controlled centrally to avoid congestion or to close lanes following collisions.

Many smart motorways have expanded to four running lanes instead of the more traditionally known three, or use the hard shoulder as a running lane during busy operational hours. 

Where the latter has been implemented, National Highways is working to implement emergency refuge areas. 

These are areas of safety, often shown with yellow tarmacked areas. As of 2024, these are still being implemented.

Image of 'smart' motorway, showing 40mph speed limit on overhead gantry

How does a smart motorway prevent traffic bunching?

Like management systems in other industries - waterways, office work, production- it’s all about flow, ensuring that vehicles of all kinds are kept moving, no matter the speed. It’s ultimately better for traffic to be on the move, rather than static.

They are called ‘smart’ because ‘smart motorways’ use data and judge road conditions to make active changes, giving clear instructions to drivers. They are proven, according to our friends at National Highways, to be safer than more traditional motorways.

There are multiple ways in which a smart motorway prevents traffic congestion or potential stoppages on the motorway network.

Variable speed limits

The most common use of smart motorways is the implementation of variable speed limits. 

By splitting the motorway into ‘zones’, the flow of vehicles can be controlled to prevent bottlenecking or overwhelming between junctions. 

Sensors in the road monitor the traffic flow and speeds change automatically to keep the traffic moving.

Simply, by making some areas have a higher speed limit than others, traffic 'at the front’ can be cleared quicker and the motorway returned to normal more smoothly.

Dynamic lane management

By using the same radars to monitor speed, dynamic lane management measures capacity or spots potential dangers to open or close lanes and spread traffic.

Basically, more room for more vehicles to prevent vehicles from bunching. This ultimately reduces the risk of further incidents.

What does the red cross mean on a smart motorway?

If you want to avoid a fine and, potentially, at worse, a driving ban, then look out for the red crosses on the overhead gantry.

This means that a lane is closed and there is potentially danger ahead. Driving in a closed lane could result in a fine of up to £100, three points or a potential court appearance where harsher penalties could be dealt.

The implementation of smart motorways means that lanes can be closed for safety within less than 60 seconds, rather than the more traditional method of cones and physical signage. 

It’s more financially efficient than getting a team to do this in the middle of the night, too!

How many smart motorways in the UK?

Currently across the United Kingdom, there are 13 motorways that can be defined as a ‘smart motorway.’

These are:

  • M1 - Four sections of the M1 have smart technology installed, with the longest stretch between J6A and Junction 10.
  • M6 - The run between J10A - J11A have the smart motorway capability. You’ll experience a small amount of this if you’re heading to Roadchef Norton Canes!
  • M8
  • M9
  • M20 - Before you get to Roadchef Maidstone at Junction 8 of the M20, you’ll pass through a run of smart motorway between Junction 5 - 7.
  • M25 - As you leave Roadchef Clacket Lane Eastbound, you’ll enter a section of Smart Motorway that operates between Junction 6 and Junction 7.
  • M40
  • M42 - The first smart motorway trial took place on the M42
  • M60
  • M62
  • M73
  • M74
  • M90
  Time to be smart and take a Roadchef break? Check our your nearest Roadchef location