general image

How Do Speed Cameras Work?

Author of the article

By Saoirse McClure Fisher

calendar 25-10-2021 tag MAINTENANCE clock 5 min read

The real answer? Probably too well. There is no worse feeling than driving along and seeing that telltale flash. The best way to avoid being flashed is to drive under the speed limit, but knowing how speed cameras work can help you avoid falling foul of a hefty fine (and possibly points on your licence). Today we will tell you all you need to know.

Types of Speed Cameras

There are several types of speed cameras found on UK roads. Here are the types you'll most commonly encounter: -

Fixed Speed Cameras

This type of camera is very common. It is normally a large yellow box mounted on a beam or arm. The camera is activated by two pressure sensors placed at a given distance on the road. Cross that distance too quickly, and the camera is activated.

These cameras can be swivelled to face either direction and are also capable of taking pictures of oncoming traffic, so no getting out of it by saying you weren't at the wheel!

Mobile Speed Cameras

These are a firm favourite in areas that don't get a high density of traffic. These cameras are operated by a traffic officer or policeman. 

They work by directing a laser beam onto the vehicle. A clever 'radar gun' detects how long the beam takes to hit the vehicle and bounce back. This is repeated, and the vehicle's speed is calculated using this data.

Mobile camera vans take pictures, but occasionally you'll see a policeman standing on an overhead bridge. If you are found to be speeding, you can expect to be pulled over further down the road.

Average Speed Cameras

Average speed cameras are used in areas with a fixed speed. Two cameras are used. Each car numberplate is filmed and logged using ANPR technology. From there, a computer measures how long it takes the same car to reach the second camera.

If a car does this in a time quicker than the speed limit allows, a picture is taken, and then the driver is fined accordingly.

These cameras are very popular on temporary roadworks on motorways (so you'll see a lot on UK roads.)

Oh, and top tip… Don't think changing lanes will save you. The computer controlling the cameras is smart enough to determine which vehicle is which by scanning the number plate.

Variable Speed Cameras

Variable speed cameras are like a cross between fixed speed cameras and average speed cameras. They can log and flash drivers using a single camera and calculate average speed (so no zooming between each camera).

They are predominantly used on smart motorways.

The main difference between variable speed cameras and average speed cameras is that the speed limit can change. So, it pays to pay particular attention to the overhead speed limits and slow down if you notice the change.

What is the Maximum Speed I Can Drive at without Being Caught?

Now, it is time to put to bed a common myth.

You'll hear people stating all sorts of complex formulas. Things like "as long as you are within 10% you are ok" or "is 10mph over the speed limit".

Neither of the above is true.

The truth is that if you are even one mile per hour over the speed limit, you are breaking the law and can be fined accordingly.

The 'official' triggers for speed cameras are not published. Why? This would, in effect, become the new 'unofficial' speed limit. 

How Do You Know if a Speed Camera Caught You?

The most obvious sign that you have been caught by a speed camera is a flash. This is normally pretty obvious, but there are circumstances where you won't see a flash. On bright days some cameras are calibrated not to flash. Also, certain speed cameras have their flash muted and diffused to avoid startling drivers (yeah, thanks).

If you have fallen in the sights of a policeman's radar gun, the time you know about it is when you are being pulled over by their colleague further down the road.

The only way to be sure that a speed camera hasn't caught you is to avoid going over the speed limit in the first place.

Can Speed Cameras Catch You from the Front?

Speed cameras can catch you from the front.

There is a type of camera called a Truvelo Combi that is purposefully designed to be able to catch speeding drivers from the front. 

If you are intercepted by a mobile speed camera, the readings are also taken head-on, although depending on whether it is 'van mounted' or 'handheld', they may not take a picture.


Slowing it Down…

The best way to avoid being caught speeding is to drive slower. Do you know the best way to make sure that you can reduce your speed when you need to? A new set of tyres. By maintaining a better grip, you'll have more control over your vehicle and will be able to slow down quicker.

Motokiki is a great online service for sourcing new tyres. By entering your registration, you can quickly and easily source the perfect tyres for your exact vehicle. Why not enter your registration now or search for a local fitter? New tyres are cheaper than speeding tickets! 

Share this article:


Get more with our tyre comparison

Get the best tyre prices and buy now from independent fitters near you!

  • Search postcode

  • Search tyre size