How do average speed cameras work?

It’s a topic that divides the nation: speed cameras. Some see their benefits at increasing road safety and keeping both drivers and pedestrians safe, whereas others see them as nothing more than a cash grab – extorting more money from drivers who are already seeing price rises across the board.

It’s estimated that there are around 7,000 speed cameras in the UK, that’s the fourth highest number of anywhere in the world, with only Brazil, Russia and Italy having more cameras.

The UK’s first speed camera was installed on the M40 in 1991 – the Gatso camera is a common sight on UK roads, with around 4,000 of them. We all know the one – it’s the big yellow box that almost looks like a certain robot from a famous sci-fi franchise…

Yellow average speed camera

But Gatso cameras aren’t the focus of this article. Today, we’ll be looking at arguably the most opinion-dividing speed cameras of them all: average speed cameras. But how do they work? Let’s dive in.

What are average speed cameras?

Average speed cameras can be a temporary fixture in areas that are undergoing long stretches of roadworks, or a permanent addition to the side of the road. To look at, average speed cameras are generally taller than other types of speed cameras, painted fully in yellow and covering multiple lanes with different cameras covering each of those lanes.

Where are average speed cameras?

Average speed cameras can be located on many different road types. They can be placed on motorways as well as A roads. The official line is that average speed cameras are put on location in areas where traffic speed has been seen as something of a concern.

Councils will generally perform a survey on the road before introducing cameras to see what speed on a particular stretch is looking like. Look out for two lines of wire across the carriageway which could be a survey that is monitoring speed but doesn’t single out the driver. If a certain threshold is hit during the survey, a camera could be installed at that location.

Average speed check sign

Do average speed cameras flash?

That feeling of dread as you pass a typical Gatso speed camera and it flashes at you is absent from average speed cameras. This variation of camera doesn’t flash and uses infra-red technology instead, meaning you won’t know if you have been caught or not – until your letter comes through the post that is.

How do average speed cameras work?

Whether it’s a temporary speed limit or a permanent road limit, average speed cameras work very much in the same way. They measure your speed and how long it takes your vehicle to get between two points – those points being each camera.

Average speed example

As an example, let’s take an average speed zone of 10 miles with a speed limit of 70mph (a motorway being a road type that would allow this).

If you pass the first camera at 50mph, and then the last camera at that same speed, but it only took your vehicle 8 minutes to complete the full 10 miles, your average speed works out to be 75mph. As your average speed over the course of the average speed zone is 75mph, you will receive a speeding ticket.

Average speed camera

What is the average speed camera tolerance?

Research conducted in 2021 by Auto Express showed that cameras do have a tolerance, but it varies depending on the area of the country you live in. Some police forces wouldn’t reveal the threshold, while others said that the tolerance is 10% + 2mph – some also said 10% + 3mph.

This is a difficult question, because there is a lot of misinformation out there on the internet. It’s important to remember that anything over the speed limit is breaking the law – whether that be 1mph or 10mph.

Want to know more about the meanings of our different road signs? Check out our helpful blog article, and if you’re searching for high-visibility chevrons, our range is fully Chapter 8 compliant.