What is a smart motorway and how do they work?

Despite their high-speed limits and the sheer volume of traffic they carry, motorways are considered to be the safest roads in the UK. According to the RAC, more deaths occur on country roads than on motorways.

With that in mind and the fact that more than 25 million people live in a household that owns at least one car, it’s not surprising that motorways are busier than ever. However, having more vehicles on motorways means that the government needs to invest time and money to make them as safe and efficient as possible.

Aiming to reduce congestion, smart motorways were introduced in 2006 by Highways England (previously called the Highways Agency). Today, they make up around 15 per cent of the UK’s 2,300-mile motorway network.

But what is a smart motorway, and how does it differ from a conventional motorway? In this article, we explain what smart motorways are, go through their pros and cons and give details of where they’re located.

Contents

What is a smart motorway, and how do they work?

Smart motorways are motorways that feature various technologies to regulate the flow of traffic and reduce congestion in especially busy areas.

Some of the traffic management methods used on smart motorways include turning the hard shoulder into an additional lane, variable speed limits and sensors that measure traffic flow and detect stationary vehicles.

Continue reading to find out more about smart motorways.

What are the different types of smart motorways?

There are three types of smart motorways, each of which has slightly different characteristics:

All lane running motorway

These are the most common types of smart motorways and, as the name suggests, all lanes are running lanes — including the hard shoulder, which has been permanently converted into an extra lane. To fulfil the role of the hard shoulder, emergency refuge lay-bys are provided at regular intervals.

Variable speed limits — which are signalled on overhead gantries and enforced by speed cameras — are used to control traffic flow when there’s congestion or if there’s a hazard ahead.

In the event of a hazard, one or more lanes could be closed, which will be indicated by a red ‘X’ on gantries or verge-mounted signs.

CCTV cameras are also used on all lane running motorways to monitor traffic for incidents. They can detect a vehicle that’s broken down or been involved in an accident.

Dynamic hard shoulder motorway

Like all lane running motorways, dynamic motorways have a hard shoulder that is used as an extra lane for traffic. The difference is that the hard shoulder only turns into an additional running lane when traffic is heavy, and motorists should only drive on them when overhead gantries instruct them to do so.

Controlled motorway

Controlled motorways differ from the above two smart motorways, in that they have a permanent hard shoulder.

What makes them smart motorways is that they have sensors on the road to measure traffic volume and feature variable speed limits displayed on overhead gantries, which change according to traffic conditions in order to control the flow. Like the other two types of smart motorways, these variable speed limits are enforced by speed cameras.

How do you know you’re on a smart motorway?

As mentioned above, smart motorways have certain characteristics that distinguish them from conventional motorways.

If you’re driving on a motorway and the hard shoulder is used as an additional running lane or the speed limit changes according to overhead gantry signs which are accompanied by small yellow speed cameras, it’s likely you’re on a smart motorway.

How fast can you drive on a smart motorway?

Unless overhead gantries specify otherwise, the speed limit that applies to conventional motorways is 70 miles per hour and this applies to smart motorways too.

It’s worth noting, though, that variable speed limits can change quickly, so to save drivers from having to slam on their brakes to reduce their speed in time, Highways England has clarified that there is a slight delay between when the speed limit changes and when the cameras start enforcing that limit. However, these time periods can be as fast as ten seconds, so drivers must remain alert and respond to changing speed limits quickly and safely.

What are the disadvantages of smart motorways?

Smart motorways were introduced as a cheaper and quicker alternative to building new motorways or widening the ones that already exist. Utilising the hard shoulder, for example, costs roughly 60 per cent less than it would cost to widen an existing motorway. It’s not just about cost, though: Some motorways can’t be widened due to their proximity to towns, cities, rivers, steep hills or mountains.

However, smart motorways are controversial because some critics question their safety and claim they have led to road deaths. This is mainly because of the lack of a hard shoulder on all lane running and dynamic smart motorways. Without a hard shoulder, vehicles can be stranded in a stream of fast-moving traffic, while emergency vehicles can struggle to reach an incident.

In 2020, the BBC reported that 38 people had been killed on smart motorways between 2014 and 2019, and although all lane running motorways haven’t been in operation long enough to provide enough data to make a fair and accurate comparison, the Department for Transport has paused the rollout of these types of smart motorway for five years as a result of increasing safety concerns. Smart motorways that are already in the process of construction will still be completed, though, and existing all lane running motorways will be unaffected.

In a bid to improve the safety of smart motorways, the following measures have either been taken or are scheduled to be taken:

Increase the number of emergency refuge areas to shorten the distance between each lay-byIncrease the number of signs advising motorists how far it is until the next safety spotIncrease the number of systems that automatically detect vehicles that have stopped in running lines (by September 2022 this technology is due to be standard across all lane running smart motorways)Paint emergency refuge areas orange to make them more visibleRun communication campaigns to educate motorists on how to drive on smart motorways, with an emphasis on the importance of obeying red ‘X’ signs Upgrade motorway speed cameras to allow them to detect vehicles driving in closed red ‘X’ lanes

What are the rules for driving on smart motorways?

All of the usual road laws and rules apply on smart motorways, but because of their inconsistencies, it is worth clarifying the following points:

A broken white line indicates a normal running laneA solid white line indicates the hard shoulder, which should never be crossed unless instructed to do soBe aware of the vehicles all around you — especially when changing lanes — and don’t just base your decisions on what the driver in front of you is doingIndicate to let other road users know that you’re changing lanesLeave plenty of space between you and the vehicle in frontNever drive in a lane that’s indicated by a red ‘X’ as closedStick to the speed limit that’s shown on the overhead gantries and adjust your speed depending on traffic and weather conditionsUse the lefthand lane unless you’re overtaking or allowing other motorists to join the road

As with other roads, you can be fined for committing motoring offences on smart motorways. Some of the most common motoring offences on smart motorways are for:

Speeding — There are more cameras on smart motorways and speed limits can vary, meaning the chance of getting a speeding ticket is much higher.Ignoring red ‘X’ signs — Driving in a red ‘X’ lane is extremely dangerous and illegal. Motorists who disobey this rule face three penalty points on their driver’s licence and a £100 fine.

Where are the UK’s smart motorways located?

The first smart motorways as we know them were introduced in 2006, but the first sections of controlled motorway were introduced on the M25 as early as the 1990s.

Today, almost the entire route around London consists of either controlled or all lane running sections and there are around 375 miles of smart motorway in England — 235 miles of which lack a hard shoulder. The government plans to increase this to nearly 800 miles by 2025.

Currently, smart motorways are found in the following places:

All lane runningDynamic hard shoulderControlledM1J13 to J16 (under construction), J16 to J19, J24 to J25, J28 to J31, J32 to J35a and J39 to J42J10 to J13J6a to J10, J23a to 24, J25 to J28 and J31 to J32M3J2 to J4aM4J3 to J12 (under construction)J19 to J20M5J4 to J6J15 to J17 M6 J2 to J4 (under construction), J10a to J13, J13 to J15 (under construction) and J16 to J19J4 to J10aJ10a to J11aM20 J3 to J5 (under construction) J4 to J7M25 J5 to J6/7 and J23 to J27 J2 to J3 and J7 to J30M23J8 to J10 M26 J16 to J23M27J4 to J11 (under construction) M40 M42 J3a to J7J7 to J9M56J6 to J8 (under construction)M60 J8 to J18M62 J10 to J12 (under construction), J18 to J20 and J25 to J26J23 to J30J28 to J29 Current smart motorways in the UK

Summary

Smart motorways are motorways that feature various technologies to regulate the flow of traffic and reduce congestion in especially busy areas. There are three types of smart motorways, each of which has slightly different characteristics:

All lane running motorwayDynamic hard shoulder motorwayControlled motorway

You’ll know you’re on a smart motorway if the hard shoulder is used as an additional running lane or the speed limit changes according to overhead gantry signs which are accompanied by small yellow speed cameras.

All of the usual road laws and rules apply — meaning you can be fined for committing driving offences on smart motorways — but it’s important to remember that:

A broken white line indicates a normal running laneA solid white line indicates the hard shoulder (which should never be crossed unless instructed to do so),You should never drive in a lane that’s indicated by a red ‘X’ as closedYou should stick to the speed limit that’s shown on the overhead gantries

What is a smart motorway and how do they work?

What is a smart motorway, and how do they work?