On a smart motorway, a speed limit shown in a red circle is mandatory, a red X means a lane is closed, and a blank sign does not cancel a lower limit. The national limit for cars on a motorway stays 70 mph, but signs can lower it at any moment. National Highways says around 25 per cent of the motorway network is now made up of smart motorways, so these signs are worth knowing well.
| Sign | Meaning | What to do |
|---|---|---|
| Speed limit in a red circle | Mandatory limit | Keep to it, whatever the reason |
| Speed limit with no red circle | Maximum speed advised for the conditions | Slow down to suit the conditions |
| Red X, or red flashing lights | Lane closed | Move to an open lane; you must not drive in it |
| Flashing amber lights | Hazard ahead | Reduce speed and be ready for the hazard |
| Blank sign | Previous instruction still applies | Keep to the lower limit |
| National speed limit symbol | National limit restored | 70 mph is the maximum for a car, if conditions allow |
| "END" or a speed limit after a red X | Lane no longer closed | The lane can be used again |
| Speed limit above the hard shoulder | Hard shoulder open as a lane | You can use it as a lane |
| Red X or blank sign above the hard shoulder | Hard shoulder closed as a lane | Emergency use only |
What is a smart motorway?
A smart motorway is a motorway that uses technology such as overhead signs and variable speed limits to manage traffic, and there are three types. The Department for Transport describes them in its comparison report:
What is a controlled motorway?
A controlled motorway keeps the conventional layout, including the hard shoulder, and adds technology such as variable speed limits and overhead signs. Some have also been widened to add a lane.
What is a dynamic hard shoulder motorway?
A dynamic hard shoulder motorway uses the same technology and opens the hard shoulder as a running lane at peak times. National Highways lists sections of this type on the M62, M42, M6, M1 and the M4 and M5 around Bristol, covering 63 miles in all. These motorways also have emergency areas.
What is an all lane running motorway?
An all lane running motorway permanently converts the hard shoulder into a running lane. In its place, there are emergency areas and technology that detects stopped vehicles.
What do the signs on a smart motorway mean?
The signs on a smart motorway tell you the limit, which lanes are open and whether there is a hazard ahead, and the colour and shape tell you how firm the instruction is. The table at the top of this article gives you the short version. Signs can apply to the whole carriageway or to a single lane, so always read the one above your own lane.
Is a speed limit in a red circle mandatory?
Yes, a speed limit in a red circle is mandatory, and Highway Code rule 261 says you must not exceed it. National Highways says it remains enforceable whatever the reason for it, even if that reason is not obvious to you.
What does a speed limit without a red circle mean?
A speed limit without a red circle is advice rather than a legal limit. The Department for Transport describes these as the maximum speeds advised for the prevailing conditions, so treat them as a clear warning that something ahead calls for a slower pace.
What do flashing amber lights on a motorway mean?
Flashing amber lights warn of a hazard ahead. Rule 257 says you should reduce your speed and be prepared for the hazard, and only speed up again when you pass a signal that is not flashing, or a sign displaying a national speed limit or the word "END", and you are sure it is safe. On older signals, mainly in Scotland, the Department for Transport advises not exceeding 30 mph until you have passed the hazard.
What does a red X mean on a motorway?
A red X means that lane is closed, and you must not drive in it. Highway Code rule 258 says a closed lane is one in which people, stopped vehicles or other hazards are present, so the lane can look empty from a distance and still not be safe.
Here is what to do when you see one:
- Follow the signs ahead of the closed lane and move safely to an open lane.
- Stay out of the closed lane, even if you cannot see the reason for the closure.
- Wait for a sign showing a speed limit or the word "END", which tells you the lane is no longer closed.
A few details are easy to miss:
- Emergency services and traffic authorities use closed lanes to reach incidents and help people in need.
- Where the left lane is closed at an exit slip road, that exit cannot be used.
- Where red flashing lights and a closure of all lanes are shown, the road is closed. You must not go beyond the sign in any lane unless directed by a police or traffic officer.
- The police enforce lane and road closures, and National Highways says enforcement cameras have been upgraded to detect vehicles passing under a red X or entering a lane beyond one.
How do variable speed limits work?
Variable speed limits are limits that National Highways changes on England's motorways and major A-roads, shown on illuminated electronic signs at the roadside or on gantries over the lanes. They are designed to improve safety and keep traffic moving, and the signs are designed to be readable from at least 300 metres.
Why does the speed limit change on the motorway?
The limit can change for several reasons, and it may not always be obvious which one applies. National Highways lists these:
- traffic congestion, either actual or expected
- roadworks
- traffic officers working nearby
- extreme weather
- incidents
What happens when the motorway signs go blank?
A blank sign means the previous instruction still applies, and it does not cancel a lower limit. National Highways says lower limits stay in force until you pass a national speed limit symbol, which shows the national limit has been restored. If that symbol fails to appear because of a fault, keep to the lower limit until you see it.
Are variable speed limits enforced by cameras?
Yes, on sections marked with camera signs. The cameras record an image, the registration number, speed, date, time and the limit on display, and that data goes directly to the responsible police force. The equipment is Home Office type approved, and Police Scotland explains that one such system, HADECS, uses calibrated radar to measure each vehicle passing a gantry. The Highway Code shows the "Variable speed limit with camera enforcement" sign, so look out for it.
Does a camera flash mean you were speeding?
Not necessarily. National Highways says enforcement equipment runs a self-check when a limit changes, which may cause a flash, and that this does not necessarily mean your vehicle was detected.
Which limit applies at roadworks on a smart motorway?
Temporary metal signs at the roadside usually show the limit, with blank gantries through the works, and in exceptional cases electronic signs inside the works may show a variable limit. National Highways says that if you are unsure, you should follow the lower limit. Many of these sections use average speed cameras.
Can you drive on the hard shoulder of a smart motorway?
You can only use the hard shoulder as an extra lane when a speed limit is shown above it. Highway Code rule 269 is clear on the rest:
- A red X or a blank sign above the hard shoulder means you must not use it except in an emergency.
- On a motorway where the hard shoulder is not used as a lane, you must not use it except in an emergency, or if directed by the police, traffic officers or a traffic sign.
- Where the hard shoulder is used as an extra lane, emergency areas are provided for use in an emergency.
What should you do if you break down on a smart motorway?
Move left and get to a place of relative safety if you can, then call for help. National Highways summarises its advice as go left, get safe, get help. If possible, leave the motorway at the next exit or pull into a service area, and do not stop in a live lane unless absolutely necessary.
- Go left: move into the left lane and pull into an emergency area, lay-by or hard shoulder if you can. Stop as far left as possible, switch on your hazard lights, and use sidelights if visibility is poor.
- Get safe: if it is safe, leave on the side away from traffic and keep passengers clear of the carriageway. Do not go back to the vehicle or attempt repairs, and do not put a warning triangle on the carriageway.
- Get help: use an emergency telephone or a mobile to call National Highways on 0300 123 5000, or contact a breakdown recovery service.
What if you cannot reach a safe place?
If you cannot reach the left lane or a place of relative safety, and cannot get well away from your vehicle and the traffic, Highway Code rule 277 says to stay in your vehicle with your seatbelt fastened and hazard lights on. Call 999 straight away and ask for the police, or press your SOS button if your vehicle has one.
What is an emergency area on a motorway?
An emergency area is a place to stop on motorways with no hard shoulder, or where the hard shoulder can be used as an extra lane. Rule 270 says they must only be used in an emergency, and that they are marked by blue signs with an orange SOS telephone symbol and may have orange surfacing. To rejoin the motorway from one, rule 278 says you must use the emergency telephone and follow the operator's advice, because a lane may need to be closed first.
Are smart motorways still being built?
No, the Government cancelled plans for new smart motorways in April 2023, citing a lack of public confidence and cost pressures. The existing ones remain in use, and National Highways says plans to convert dynamic hard shoulder sections to all lane running have been cancelled too.
On safety, National Highways says data for 2018 to 2022 shows all three types have fewer deaths or serious injuries than conventional motorways. It also reports these measures as complete:
- more than 700 additional signs showing the distance to the next place to stop in an emergency
- radar stopped vehicle detection on every all lane running motorway
- upgraded cameras that detect vehicles passing under a red X
What do smart motorways mean for your next drive?
Before you join a busy motorway, keep three rules in mind. A red circle is the limit. A red X means move out of that lane. A blank sign changes nothing until you pass the national speed limit symbol. Leave plenty of space too, because traffic can slow quickly here, and our guide to Highway Code stopping distances shows how much room you need. For the limits on other roads, see our guide to the national speed limit in the UK.
Ghost is a calm companion on these roads. It warns you about known fixed speed cameras and average-speed zones about 700 m ahead and again at 250 m, with one tone and no voice, so you never have to take your eyes off the signs above you. It runs in the background next to any navigation app, works on CarPlay, Android Auto and Apple Watch, and covers more than 125,000 speed cameras worldwide. You stay in charge of the road, and Ghost quietly looks out ahead.
