Speed cameras on motorways in England do two main jobs: they enforce the variable speed limits shown on gantries and roadside signs, and they enforce average speed checks through roadworks. National Highways, a public body sponsored by the Department for Transport, provides the equipment on its motorways; the police do the enforcing. National Highways says a speed limit shown in a red circle is enforceable whatever the reason for it. This guide explains how each system works, what the signs mean and what the Highway Code says.
Variable speed limits and the cameras that enforce them
Variable speed limits (VSL) appear on illuminated electronic signs at the side of the motorway or on gantries over the lanes. National Highways says it lowers them for traffic congestion, actual or likely, roadworks, its traffic officers working in vulnerable locations, extreme weather and incidents. It adds that it does not need to give a reason for a lowered limit to be legally enforceable by the police. Rule 261 of the Highway Code says you must not exceed a limit displayed within a red circle on a sign, or the maximum limit for the road and your vehicle, and that the police enforce limits.
The Highway Code traffic signs page includes a sign for a variable speed limit with camera enforcement. According to National Highways, camera signs mark the sections of motorway where vehicle speeds may be detected.
What the equipment records
National Highways says the equipment records an image of the speeding vehicle, its registration number and speed, the time and date, and photographic evidence of the limit on display as the vehicle passes. The data goes directly and securely to the regional police force, and National Highways says it has no access to it. It also says all enforcement equipment on its roads has Home Office Type Approval.
What HADECS is
Police Scotland describes HADECS, the Highway Agency Digital Enforcement and Compliance System, as an intelligent transport system that aims to encourage compliance with mandatory variable speed limits. It uses an automatic digital camera and radar system, and the calibrated radar measures the speed of every vehicle passing the gantry. If an offence is detected, two images are taken and used to verify that the radar speed matches the distance travelled between them. The Gatso guide explains the same check on a roadside camera.
A flash and a blank sign
Two situations confuse drivers.
- A flash. When a limit or a closed lane signal changes, National Highways says the enforcement device runs a self-check and passing vehicles may see a flash. That does not necessarily mean your vehicle was identified as speeding.
- A blank sign. If a display is blank or unlit, the previous instructions still apply. A lowered limit ends only at the national speed limit symbol.
National Highways says its VSL signs are designed to be visible from at least 300 metres.
Average speed checks at motorway roadworks
At roadworks you may see a fixed limit sign with the words Average speed check. National Highways says its average speed enforcement cameras are painted yellow and have infra-red illuminators, so they work in all weather, 24 hours a day. At least two locations are needed: an entry camera and an exit camera read the number plate by automatic number plate recognition (ANPR), and the system works out the average from the known distance and the time taken.
For vehicles that stayed within the limit, National Highways says the number plate data and images are deleted automatically. For the others, the evidence record goes to the police. Our guide to how an average speed check works has the principle in detail. The DfT guidance of 2007 asks that temporary cameras to enforce lower limits at major roadworks be seriously considered.
Limits and penalties
GOV.UK gives the national limit for cars on motorways as 70 mph, and 60 mph for a car towing a caravan or trailer. The minimum penalty for speeding is a £100 fine and 3 penalty points. If you go to court, the fine is usually a percentage of weekly income, up to £1,000, or £2,500 if you were driving on a motorway. This is a summary of GOV.UK, not legal advice.
Where motorway speed cameras are
The National Highways pages read for this guide give no list of camera locations; the camera signs mark the enforced sections. National Highways also says requests for its variable speed limit settings at specific times and places are likely to be refused under the law enforcement exemption of the Freedom of Information Act. For official maps of other camera types, see speed camera locations and maps.
BlitzBuddy and motorway cameras
BlitzBuddy gives no speed camera warnings in the UK, Ireland or other countries outside the five where it warns (the Netherlands, Belgium, Germany, France and Türkiye); your speed, trips and reports from other drivers still work. In the Netherlands it also shows live overhead matrix signs from NDW, drawn lane by lane, and they are shown on screen, not spoken; the matrix signs guide explains them. In Germany, § 23 (1c) StVO forbids drivers to use a speed camera warner while driving; the warnings can be switched off under Profile, Warnings, and the driver is responsible. In France, article R413-15 of the Code de la route, in paragraph V, has since 5 January 2012 also banned devices that warn of or inform about the location of the equipment used to record traffic offences; using these warnings is the driver's own responsibility. For the other countries, read where speed camera warnings are allowed.
More guides on the same topic are collected under speed camera guides.
Sources
- Variable speed limits, National Highways
- National Highways, GOV.UK (organisation page)
- Average speed enforcement cameras around roadworks, National Highways
- Camera Type, Police Scotland Safety Cameras
- The Highway Code: general rules, techniques and advice for all drivers and riders (103 to 158), GOV.UK
- The Highway Code: Motorways (253 to 273), GOV.UK
- The Highway Code: Traffic signs, GOV.UK
- Speed limits, GOV.UK
- Speeding penalties, GOV.UK
- DfT Circular 01/2007: Use of speed and red-light cameras for traffic enforcement, Department for Transport (pdf)
- Straßenverkehrs-Ordnung, § 23, Federal Ministry of Justice (in German)
- Code de la route, article R413-15, Légifrance (in French, version in force since 5 January 2012)
Sources read on 11 October 2026.
Frequently asked questions
Do motorway speed cameras flash?
Sometimes. National Highways says that when a speed limit or lane signal changes, the enforcement device runs a self-check and passing vehicles may notice a flash. That does not necessarily mean your vehicle was identified as exceeding the displayed limit.
Are there speed cameras on smart motorways?
Yes. National Highways says it provides speed detection equipment for variable speed limit enforcement, and camera signs mark the sections where speeds may be detected. The police enforce the limits.
What if the speed limit sign above the motorway is blank?
National Highways says a blank or unlit display means the previous instructions must still be complied with. A lowered limit continues until you pass the national speed limit symbol.
What is the speed limit on a motorway for a car?
GOV.UK gives 70 mph for cars on motorways, 60 mph for a car towing a caravan or trailer. National Highways says a variable limit displayed in a red circle must always be complied with, whatever other gantries show.
How are speed limits enforced at motorway roadworks?
Where a fixed limit sign is shown together with the words Average speed check, National Highways says vehicles exceeding that limit are detected by average speed enforcement cameras.
