Speed cameras – how they work

Speed cameras are one of the most contentious points of motoring for a great many drivers.

Whether you see their benefits or not, you'll have to learn to live with them, so it is advisable to know all you can on the topic to ensure you stay safe and legal.

Speed cameras – the facts

The first speed camera – or safety camera, to use the official terminology – was installed on the A316 over Twickenham Bridge in 1992.

It was a Gatso device, and the trigger speed was set at 60mph: the A316 had a 40mph speed limit.

22 days after being turned on, it caught nearly 23,000 drivers speeding at over 65mph.

There are currently around 7,000 speed cameras spread out across the country.

How do speed cameras work?

Speed cameras work by recording a vehicle’s speed. It does this by using markings on the road or radar technology to identify the vehicle and record its speed. 

Older cameras used film to record speeding offences, but advances in technology has resulted in speed cameras being digitised.

If a vehicle is travelling at excessive speed, two digital images are taken to work out how long it has taken the vehicle to travel between two points on the road. The images also record the vehicle’s registration, time of the offence and speed limit of the road.

In some cases, the image will include the face of the driver and the front passenger. 

Not all speed cameras will flash when they take an image of your car and some speed cameras will track your vehicle over many miles to work out its average speed. 

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Can I drive 10% + 2 above the speed limit and not get caught?

​Fixed speed cameras have a set trigger for catching people speeding, however, it is unconfirmed what most are set at so it's not worth gambling and assuming they give you 10% - never exceed the speed limit.

Mobile speeding cameras are operated by individuals, so it is up to their discretion to issue you a speeding fine - or worse - if you are over the legal speed limit.

The law states that you are liable for a speeding fine as soon as you exceed the limit, so if you’re doing 31mph in a 30 limit or 71mph on a motorway, you’re breaking the law and could receive a fine.

The National Police Chiefs’ Council (NPCC) recommends giving drivers a so-called ‘10% plus 2’ leeway, to aid police officers in using 'discretion', however, this is just a recommendation, not the law.

It is well worth remembering this is totally dependent on the officer who catches the speeder, and it is up to that officer whether to fine the offender or not.

The best advice is to not speed.

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How far away can speed cameras catch you from?

Current speed camera technology allows detailed video and images of drivers to be taken from up to one kilometre away.

Most cameras, however, use markings on the road to measure distance over time and determine your speed. SPECS average speed cameras can calculate average speed over distances between 75 metres and 20 kilometres. They appear in sequence on motorways at least 200 metres apart.

Advanced cameras capable of capturing images and videos of drivers up to one kilometre away have been nicknamed ‘Long Rangers’.

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Do speed cameras have to be visible?

All working speed camera on the strategic road network should be painted yellow, although this rule isn’t a legal requirement. 

The yellow paint scheme was introduced in 2015 following a review by ministers, with the Government saying it would improve speed camera visibility to ensure motorists were not unfairly penalised.

Some speed cameras can still be difficult to spot, especially mobile units, but the yellow cameras are considered by many to be a significant improvement over the old, grey cameras.

Types of speed cameras

There are many different types of speed camera on the market, but in the UK, a few key types are most common.

Fixed speed cameras

The Gatso was the first speed camera to be installed in the UK and has become the most commonly used camera on UK roads.

Back in 1992 they were painted grey, but a change in the law meant that they have to be painted bright yellow.

The rear-facing Gatso might be the most ‘popular’ camera on the road, but it’s accompanied by the Truvelo, which uses a forward-facing camera to catch speeding motorists.

Unlike the Gatso, it photographs the driver at the wheel, meaning there’s no disputing who was at the wheel at the time of the offence.

Mobile speed cameras

The majority of these are run by local police forces and reside on accident blackspots where there is a history of road traffic incidents over a three year or more period.

There are also mobile speed cameras used as part of safety camera partnership teams and speed safety campaigns.

These cameras can take on a number of forms, working from marked or unmarked cars, as well as being manually operated by police officers using radar guns and laser guns.

There are many FAQs about mobile speed cameras, especially radar guns, so we have answered a few of the most common queries below.

How do average speed cameras work?

Average speed cameras use automatic number plate reading (ANPR) technology to record your speed between two points on a road. The cameras also record the date and time as you pass between each point, enabling the camera to calculate your average speed.

Introduced in 1999, average speed cameras are a common sight on UK roads. You’re also likely to encounter these cameras at roadworks, as well.

Variable speed cameras

Variable speed cameras work in a similar way to average speed cameras, but they’re unlikely to be in operation 24/7.

They tend to be used on smart motorways when the speed limit is lowered to ease congestion or in the event of poor weather or some other hazard.

The speed cameras are situated on the overhead gantries and the limit will be displayed on a series of signs.

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Traffic light cameras

Traffic light cameras detect vehicles which pass through lights after they’ve turned red by using sensors or ground loops in the road.

When traffic lights are on red, the system becomes active and the camera is ready to photograph any car that passes over the trigger.

It’s an offence for any part of your vehicle to pass the white stop line if a traffic light has turned red.

The vast majority of red light cameras in the UK are made by Gatsometer.

These Gatso RLC 36 units also have built-in radar technology, with dual speed and red light functions, so for the sake of safety and the law, avoid the temptation to put your foot down when they start to change.

Two-way speed camera

In June 2023, a new type of speed camera was introduced in Devon and Cornwall - with aims of it being introduced more widely across the UK.

New 'bi-directional digital cameras' will replace older speed cameras on roads where there is an increased number of accidents and drivers who are caught speeding.

They are mounted on a tall silver and yellow pole with a camera pointed in opposite directions.

Radar speed cameras

A new type of speed camera is being piloted in London in April 2026 as part of an effort to cut speeding across the capital.

Developed in partnership with Transport for London (TfL) and the Metropolitan Police Service (MPS), the system uses advanced 4D radar technology paired with a 4K colour camera. It operates without the need for visible flashes, white lights, in‑road sensors or painted markings.

Unlike existing cameras, which typically monitor up to three lanes in a single direction, this next‑generation device can track traffic travelling in both directions across as many as five lanes.

The cameras will be installed in Haringey, Tower Hamlets, Havering, Croydon, Hammersmith and Fulham, Brent, Hackney, Ealing and Sutton.

These locations, all with 20mph or 30mph limits, were chosen by TfL based on risk levels and site suitability.

Are speed camera detectors legal?

There are no laws banning speed camera detectors in the UK, although they are illegal (even as a built-in feature of your sat-nav) in many countries in Europe. 

Speed camera detectors let users know where speed cameras can be found as they travel. They tend to come in two forms; devices designed to sit on dashboards, or through route planning apps on smartphones.

The detectors use GPS technology to manually update speed camera locations through their own experience, or by downloading online data.

Jammers that ‘block’ the signal from police speed cameras are against the law in the UK and many other countries, and using one could see you slapped with massive fines. Read more about speed camera detector fines in Europe. If you'd like cover for your vehicle if you break down in Europe, check out the RAC's European breakdown cover product now.