Using Smart Motorways: A Practical UK Guide
Red X signs, changing speed limits and emergency areas can catch drivers off guard. This guide explains what the signs mean and what to do if something goes wrong — in straightforward language.
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What is a smart motorway?
Smart motorways use traffic sensors, electronic signs and variable speed limits to help manage traffic. Some have a hard shoulder that opens to traffic when signed; others use all lanes for normal driving, with emergency areas provided along the route.
They are mainly associated with England's strategic road network. The rules shown here use the Highway Code for Great Britain; Northern Ireland has its own Highway Code.
An interesting change: plans for new smart motorways were cancelled in 2023. Existing routes remain in use, so it is still important to understand their signs and safety procedures.
How to use a smart motorway safely
Explore the cards for practical explanations and relevant Highway Code rules.
Watch the motorway signs
They can change as conditions change.
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Overhead and roadside signs may warn you about queues, hazards, lane closures or a temporary speed limit. Look well ahead and follow the instructions shown.
Good habit: Check signs regularly rather than relying only on your sat-nav.
Highway Code Rules 256–258 and 261.
A red X means the lane is closed
Never use a lane showing a red X.
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Move safely into an open lane before the closure. Do not move back into the closed lane until signs show it has reopened — even if you cannot see the reason it was shut.
This is a legal requirement, not just advice.
Highway Code Rule 258.
Know when a hard shoulder is open
A solid white line does not mean a permanent driving lane.
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On some sections, the hard shoulder can become an extra lane only when a speed limit is displayed above it. If the sign is blank or shows a red X, do not use it unless there is an emergency.
On all-lane-running sections, there is no permanent hard shoulder.
Highway Code Rule 269.
Follow the displayed speed limit
A red-ringed speed limit is compulsory.
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Variable limits help manage traffic. Never exceed the speed shown inside a red circle, even if the road appears clear. Leave enough space for the vehicles ahead.
Highway Code Rule 261.
Recognise emergency areas
Look for a blue sign with an orange SOS symbol.
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Emergency areas are for emergencies only. They may have orange road surfacing. If you stop in one, use the emergency phone if available or call National Highways and follow its advice before rejoining.
Highway Code Rules 270, 271 and 278.
What if your vehicle starts failing?
Get somewhere safer, if you can.
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If possible, leave at the next exit or pull into motorway services. If that is not possible, move left into an emergency area or onto a hard shoulder where one exists, switch on hazard lights and follow the safety steps below.
Never assume an emergency area is a fixed distance away.
Highway Code Rules 275 and 277.
If you cannot get out safely
Stay belted in and call 999.
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If you are stopped in a live lane, or cannot safely leave the vehicle and get well away from traffic, keep your seatbelt on, leave hazard lights on and call 999 immediately asking for the police.
If you can safely exit away from traffic, move behind a barrier where possible, stay away from moving vehicles and do not try to repair your car at the roadside.
Highway Code Rule 277; National Highways breakdown advice.
Rejoining from an emergency area
Speak to National Highways first.
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Do not pull straight out of an emergency area. Use the SOS phone or call National Highways on 0300 123 5000 and follow the instructions given so traffic can be managed for a safer re-entry.
Highway Code Rule 278.
Keep left unless overtaking
The usual motorway lane discipline still applies.
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Use the left lane when it is clear, overtake safely, then return left. Check mirrors and blind spots before moving between lanes. Do not make sudden lane changes to avoid a closure.
Highway Code Rules 264–267.
Sat-nav alerts are helpful — not authoritative
Real road signs always come first.
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Apps can offer useful traffic and route information, but updates may be delayed or incomplete. Follow current motorway signs, not an older speed limit shown on a screen.
Smart motorway facts worth knowing
Three quick facts that explain how the network has developed.
Did you know?
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The M42 in the West Midlands hosted early active traffic management trials that opened to traffic in 2006. The approach helped inform later smart motorway designs.
What changed?
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In April 2023, the government cancelled plans for new smart motorway schemes. Existing sections remain in use, with safety improvement programmes.
Red X = closed
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You must not use a lane closed by a red X, even when you cannot see a breakdown or other hazard ahead.
What would you do?
Open each everyday scenario to reveal a safe answer.
You see a red X over the left lane. What should you do?
Reveal the answer
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Move to an open lane when safe and stay out of the closed lane until signs reopen it. (Rule 258.)
Your car stops in a running lane and it is unsafe to get out. What now?
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Stay inside with your seatbelt and hazard lights on, call 999 immediately and ask for the police. (Rule 277.)
Can you use a hard shoulder when its overhead sign is blank?
Reveal the answer
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Not as a normal driving lane. On a dynamically managed hard shoulder, it is only open when a speed limit is displayed above it. (Rule 269.)
Watch: How smart motorways work
See how smart motorways manage traffic, what motorway signs mean and how drivers can use these roads more safely in this National Highways video.
If the video cannot play here, you can use the button below to watch it on YouTube. The video is from National Highways; Motor Bridge UK does not produce or control its content.
Watch the original video on YouTubeStay informed. Stay safer.
A changing motorway sign is more important than your usual route or the speed shown on your sat-nav. Know what a red X means, recognise emergency areas and plan ahead before setting off.
If you need roadside assistance, Motor Bridge can help you explore breakdown and recovery options.
Explore Breakdown & RecoveryFor official advice: National Highways motorway guidance · Highway Code motorway rules · Breakdowns and incidents