Smart motorways – what are they, how safe are they, and why do they exist?

June 08, 2022 by

The UK’s motorway network has been transformed by the introduction of smart motorways, but what are these controversial roads, and what are their pros and cons?

‘Smart’ has become a bit of a buzzword in recent years. First there were smartphones, then came smart TVs, smart fridges, smart watches – and much more besides.

It wasn’t long before road planners got in on the action, with the UK’s first smart motorway appearing in 2006 – although the technology behind the roads existed before then. Today, smart motorways represent about 15% of our 2,300-mile motorway network, with around 375 miles of such roads having been built by the start of 2021.

But smart motorways have been dogged with controversy almost since the day they started appearing, and the safety of these roads has been the subject of countless newspaper articles and TV news pieces, as well as government investigations and ‘stocktakes’.

But what are smart motorways, why do they exist, how do they differ from less smart motorways and what should you do if you break down on one?

What is a smart motorway

Smart motorways feature a variety of technologies that aim to reduce congestion without the road having to be expanded or rebuilt at great expense. Smart motorways tend not to be complete lengths of individual motorways, but rather specific sections of existing road.

Not all smart motorways have the same set of systems, but the technologies featured include:

  • Variable speed limits (present on all smart motorways)
  • Sensors that measure traffic flow and can detect stopped vehicles
  • Lanes that can be closed, indicated by red ‘X’ signs on overhead gantries
  • Hard shoulders that can be turned into live lanes for traffic
  • Emergency refuge laybys in place of hard shoulders
Variable limits are enforced with speed cameras

Types of smart motorway

There are three different types of smart motorway, and each works in a slightly different way.

All lane running motorway (ALR)

This is an example of an all lane running smart motorway; note the lack of hard shoulder

All lane running smart motorways do not have a hard shoulder, with the lane that was previously a hard shoulder permanently converted to a live lane for traffic. Emergency refuge laybys at regular intervals fulfil the role previously played by the hard shoulder. All lane running smart motorways are the most common type of smart motorway. An example of an all lane running motorway is the M3, between Junctions 2 and 4a.

Dynamic hard shoulder motorway

These types of smart motorway have a hard shoulder that can be turned into a live traffic lane by electronic road signs when traffic is heavy and more road capacity is needed. By default the hard shoulder is not a live lane, though, and it must only be driven on when signs indicate it should be. The M1 between Junctions 10 and 13 features a dynamic hard shoulder.

Controlled motorway

Controlled motorways have a permanent hard shoulder but feature variable speed limits, which are set depending on traffic conditions.

Overhead gantries display variable speed limits on smart motorways

Although it wasn’t called such at the time, the first section of smart motorway technically appeared in 1996 between junctions 10 and 15 of the M25, when sensors in the road were introduced to measure traffic levels, and algorithms used this data to set variable speed limits enforced by speed cameras. This was an example of a controlled motorway back a quarter of a century ago and it remains one now, except it has now been extended to Junctions 10 to 16, while other sections of the M25 are also controlled motorways.

Why do smart motorways exist?

Motorways are the safest type of road in the UK. Government statistics show there were 49 accidents for every billion miles travelled on motorways in 2020, but 350 accidents – six times as many – per billion miles driven on A roads.

The inherent safety of motorways means road bosses want people to use them, but motorway congestion not only costs money in lost productivity, but can see drivers divert onto other, more dangerous types of road.

Motorways are statistically far safer than A roads

Building new motorways or widening existing ones to take more traffic is extremely expensive. Utilising the hard shoulder – either permanently, or temporarily when traffic volumes are high – creates extra capacity while costing roughly 60% less than motorway widening. Plus some motorways cannot be widened because they run past towns and cities, or close to geographical features such as rivers, or steep hills and mountains.

Smart motorway safety

Motorway drivers have become used to having hard shoulders over the years, and there can be a significant impact to their removal in terms of drivers’ perceptions of risk.

Smart motorways are, according to their critics, more dangerous than conventional ones, while a number of high-profile collisions on smart motorways have made headline news.

The roads have also received improvements – although some have argued these should have been in place as soon as smart motorways were first introduced.

Improvements include:

  • More emergency refuge areas, shortening the distance between each layby
  • More signs, advising drivers how far they have to go before they get to the next place they can safety stop
  • Emergency refuge areas have been painted orange to make them more visible
  • The rollout of systems that automatically detect vehicles that have stopped in live lanes has been increased. This technology is due to be standard across all lane running smart motorways by September 2022.
  • 96% of smart motorway speed cameras have been upgraded, allowing them to detect people driving in closed red X lanes
Emergency refuge areas are painted orange to aid visibility

Accident data for smart motorways is mixed. Department for Transport (DfT) statistics show conventional motorways actually have a higher rate of fatalities than all types of smart motorway, for example. On the other hand, the proportion of what are termed ‘slight’ casualties is higher on smart motorways than conventional ones.

The DfT’s stocktake on smart motorways concludes: “Overall, the evidence shows that in most ways, smart motorways are as safe as, or safer than, conventional motorways, but not in every way.”

Either way, in January 2022 the government paused the rollout of new all lane running smart motorways for five years so more data about their safety can be gathered; the introduction of new dynamic hard shoulder smart motorways was also previously paused. This will not reverse smart motorways that have already been built or are in the process of construction, though.

How to drive on a smart motorway

The main principles for driving on a smart motorway are the same as for driving on a conventional motorway:

  • Use the left-hand lane unless you are overtaking or need to let traffic join the road
  • Indicate to let other drivers know you are changing lanes
  • Be aware of traffic around you at all times, and especially when changing lanes
  • Do not drive based just on what the car in front is doing: look further ahead down the road
  • Drive within the speed limit, reducing your speed if traffic or weather requires
  • Leave plenty of space between your car and the vehicle in front
  • Take a break from driving every two hours.

Smart motorways do bring some additional rules, though:

  • Do not drive in a lane with a red X above it. This sign means the lane in question is closed, possibly due to a collision or broken-down vehicle. Driving in a red X lane is illegal, and cameras enforce the law, with drivers who disobey these signs face three penalty points and a £100 fine.
  • Stick to variable speed limits, which will be shown on overhead gantries and/or signs by the side of the road
  • Do not cross the solid white line and drive on the hard shoulder unless signs tell you to do so

What to do if you break down on a smart motorway

The prospect of breaking down on a motorway without a hard shoulder is frightening, but there are a number of things to bear in mind about this scenario.

The first is that cars tend not to spontaneously fail, often giving warning signs (such as a flashing engine management light, or a loss of power) before they stop working. A car travelling at 70mph can also often cruise for a significant distance should the engine fail, potentially allowing you to get to a refuge area if there is no hard shoulder.

National Highways, the organisation that runs the UK’s motorway network, advises drivers to do the following in an emergency:

Go left, coming off at the next junction if possible, or moving across the motorway to the hard shoulder or nearest refuge area. Once there, occupants should leave the car from the passenger side and get themselves behind the crash barrier and on to the verge, standing behind the car rather than ahead of it.

Drivers who break down in a live lane should stay in the car with their hazard lights and seatbelts on and dial 999.

Which motorways are smart motorways?

The following list was drawn from a map published by National Highways in 2021. Sections marked * were under construction at time of publication.

All lane running motorway

M1 Junction 13 – 16*
M1 Junction 16 – 19
M1 Junction 24 – 25
M1 Junction 28 – 31
M1 Junction 32 – 35a
M1 Junction 39 – 42

M3 Junction 2 – 4a
M3 Junction 9 – 14*

M4 Junction 3 – 12*

M5 Junction 4a – 6

M6 Junction 2 – 4
M6 Junction 11a – 13
M6 Junction 13 – 15*
M6 Junction 16 – 19

Sections of the M6 have been converted to smart motorways

M20 Junction 3 – 5

M23 Junction 8 – 10

M25 Junction 5 – 7 (ALR westbound, controlled J6-J7 eastbound)
M25 Junction 23 – 27

M27 Junction 4 – 11*

M40 – M42 interchange*

M56 Junction 6 – 8*

M62 Junction 10 – 12
M62 Junction 18 – 20

Dynamic hard shoulder motorways

M1 Junction 10 – 13

M4 – M5 interchange (M4 Junction 19 – 20 M5 Junction 16 – 17)

M6 Junction 4 – 5
M6 Junction 8 – 10a

M42 Junction 3a – 7

M6 Junction 5 – 8

M62 Junction 25 – 30 feature a mix of smart motorway types: Junction 25 to 26 and Junction 29 to 30 westbound are all lane running; Junction 26 to 28 and Junction 29 to 30 eastbound are dynamic hard shoulder; and Junction 28 to 29 are controlled motorways

Controlled motorways

M1 Junction 6a – 10
M1 Junction 23a – 24
M1 Junction 25 – 28
M1 Junction 31 – 32

M6 Junction 10a – 11a

M20 Junction 5 – 7

M25 Junction 2 – 3
M25 Junction 7 – 10
M25 Junction 10 – 16
M25 Junction 16 – 23
M25 Junction 27 – 30

M42 Junction 7 – 9

M60 Junction 8 – 18