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Smart motorways | what are they (and do they work)

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By Saoirse McClure Fisher

calendar 18-11-2020 tag MAINTENANCE clock 15 min read

It might seem counter-intuitive, but by creating variable speed limits, smart motorways might actually increase the flow of traffic. There is a lot of controversy around these relatively new traffic systems. Today we will dig into some detail (after closing off a lane or two, of course) about how they work.

What are Smart Motorways?

If you are a regular road user, there is a good chance that you have already seen a smart motorway. Large sections of Britain's major arterial routes are already in the process of being upgraded. Sections of the M6, M4 and of course, the 'revolving car-park' M25 are all smart motorways.

A smart motorway generally has two key features.

  • A variable speed limit
  • All lane running (ALR), meaning traffic, uses the hard shoulder as an 'extra' lane.

Why were Smart Motorways Introduced?

Smart motorways were introduced for a couple of reasons. Let us look above at the features:

A variable speed limit…

During times of congestion, by altering the speed limit, it is possible to ensure that traffic keeps flowing. You'll no doubt be aware that as congestion clears, people speed up in a rush to get on their way.

It may seem counter-intuitive, but road users continue to create congestion by speeding up as they may be forced to brake more often. This, in turn, causes more congestion.

By forcing road users to maintain a more constant slower speed, smart motorways prevent this 'concertina' effect. This video gives a great explanation if you want to know more about this phenomenon (and the causes for 'phantom' traffic jams).

All Lane Running…

By opening up the hard shoulder as an extra lane, the government essentially expanded the motorway's capacity without having to buy extra land.

While this might seem like a good thing in principle, there may be surprising downsides, such as a phenomenon called 'induced travel demand' . The crux of this issue is that more people use the road as there is more room to travel, leading to further congestion.

There have been scientific studies commissioned that prove this is true. If you've got five minutes, here's an example.

Also, by having no emergency refuge area, motorway traffic has no place to go if it breaks down. This may lead to a lane closure, causing the entire principle of smart motorways to come to a halt (literally)

Are Smart Motorways Dangerous?

If traffic runs smoothly without any issues, a smart motorway is no more dangerous than any other road system.


When there are issues, smart motorways can be dangerous. Here's why:

Because broken down vehicles have nowhere to go, they become an obstruction. Whereas previously you'd stand a reasonable chance of making the hard shoulder, this option doesn't exist with a smart motorway.

The end result is that broken down vehicles will have to wait for recovery by the highways agency or police. It can often take some time for a broken-down vehicle to be picked up on CCTV. And even then, while smart motorways will often give a clear indication to other drivers that the lane is closed, many road users ignore the 'red X'… Highways England issued hundreds of thousands of warning letters for this very offence every year.

It is possible to reduce the risk however, check out our tips below for guidance on how to stay safe on smart motorways…

Smart Motorway Tips | Keeping Safe

Breaking down on a smart motorway isn't the best. Here are some great tips: -

Find refuge

While smart motorways don't have a hard shoulder, there are refuge areas spaced two miles apart. If your problem isn't terminal, it is worth continuing until you can stop safely. When exiting the vehicle in a refuge area, only leave by the passenger side door.

Use your hazards

If you develop a problem, move over to the left-hand lane carefully and put your hazard lights on to indicate to other motorists that you will be stopping.

Contact the highways agency

Once you have stopped the vehicle, apply the handbrake and contact the highways agency. If you cannot reach them or need more urgent assistance, you can dial 999 and ask for the police.

Get behind the barrier

If you have reached a refuge, get out of the vehicle. And stand behind the barrier. Remember, it only takes one driver, not paying attention to cause a collision. Regardless of the weather, it's better to be safe than sorry.

Not Safe? Stay Inside!

If you are unable to reach a refuge area, follow the above guidelines. Only leave the vehicle if you can safely make your way behind a barrier. If this isn't possible, ensure that your hazard lights are on, leave your seatbelt on, and immediately call 999


Like most things, smart motorways are great when they are working. But they can be dangerous, especially when vehicles have broken down. Pay attention to the variable speed limits and overhead signs. It is worth noting where your next refuge area is too. As to whether they work, time will tell. With Britain's traffic road traffic increasing year on year, this remains to be seen.

Don’t forget, check your tyres regularly for wear, damage and foreign objects. It could avoid you having to stop on a smart motorway. If you need new tyres then search Motokiki now for a great deal.

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