How do average speed cameras work in the UK? SPECS, roadworks and permanent routes

Average speed cameras in the UK, often called SPECS, work by reading your number plate at two or more points and dividing the distance between them by the time you took. If a section is 5 miles long and takes you six minutes, your average speed is 50 mph. They need at least two camera locations, and you will meet them both at roadworks and on permanent routes such as the A9 and the A90 in Scotland.

What are SPECS cameras?

SPECS is the name many UK drivers use for average speed cameras, which measure your speed over a stretch of road rather than at a single point. National Highways describes them as yellow cameras that use Automatic Number Plate Recognition (ANPR). You will usually see them in sets along the road.

Here is how they differ from the other cameras on UK roads:

• Fixed radar cameras measure one vehicle at one point. Police Scotland explains that some record two rear-facing images about half a second apart, with painted road markings used to confirm the distance travelled.
• Variable speed cameras enforce the mandatory limit shown on motorway signs, and our guide to smart motorways covers them in detail.
• Mobile cameras are operated by trained staff, for example from clearly marked vans.
• Average speed cameras use linked cameras to measure the average speed of traffic over a stretch of road or a network of roads.

How do average speed cameras work?

Average speed cameras work by logging your number plate at each camera and calculating your speed from the distance and the time between them. National Highways sets out the process in these steps:

1. An entry camera reads your number plate and logs it.
2. An exit camera, at least one location further on, reads the same plate.
3. The system divides the known distance between the cameras by the time your vehicle took to travel it.
4. The result is your average speed for that section.

How is an average speed worked out?

The sum is distance divided by time. Take a 10-mile section with a 50 mph limit: at exactly 50 mph it takes 12 minutes. Here are a few more examples to give you a feel for it.

• 2 miles in 3 minutes is an average of 40 mph.
• 5 miles in 6 minutes is an average of 50 mph.
• 10 miles in 12 minutes is an average of 50 mph.

You never need to do this at the wheel. The simple approach is to hold a steady speed at or below the limit from the first camera to the last.

How far apart are average speed cameras?

The distance varies widely, and there is no single figure. Auto Express says sets of cameras can be as little as 200 yards apart, while a Road Safety GB report on RAC Foundation research described stretches from under half a mile in Nottingham to 99 miles on the A9.

Does slowing down at the cameras make a difference?

No, because the calculation covers the whole section, so what counts is your speed from start to finish. A brief slowdown by a camera does nothing for safety either. The aim of these zones is steady, calm traffic along the entire stretch.

Do average speed cameras work at night and in every lane?

Yes, average speed cameras work day and night and can cover several lanes. National Highways says they use infrared illuminators, so they work in all weather conditions and in the dark.

Do average speed cameras flash?

Do not expect a flash as a guide to whether they are working. Because they use infrared illuminators, these cameras are designed to work without relying on a visible light, and they log every vehicle that passes.

Do average speed cameras work if you change lanes?

Yes, a lane change makes no difference. Police Scotland says average speed cameras can face forward or backward and can record vehicles across multiple locations and lanes.

Are average speed cameras always on?

You should assume they are. Police Scotland said the temporary cameras on the A9 roadworks near Dalguise enforce around the clock, every day, and the limit applies at all times in any case.

Do average speed cameras record every car?

Yes, every vehicle's plate is logged, but National Highways says the data of vehicles within the limit is automatically deleted. What happens next depends on the result:

• Within the limit: plate data and images are automatically deleted.
• Over the limit: an evidence record with plate data, images and timestamps from both cameras goes to the police.

National Highways is not a law enforcement authority, so the police receive the data and decide what happens next. Speeding is an offence, and each camera must pass government testing so that its evidence can be used in UK courts.

Why are average speed cameras used at roadworks?

Average speed cameras are used at roadworks because temporary limits protect the people working on the road and everyone driving through it. Police Scotland's Eric Dunion made that point about the A9 dualling project in September 2026, saying the reduced limits protect road users and workers. The Highway Code is direct about it: rule 288 says you must not exceed any temporary maximum speed limit.

Which speed limit applies at roadworks?

The temporary limit on the signs applies. National Highways says the 50 mph limits around roadworks, and their end, are shown on temporary metal signs at the roadside. Electronic signs inside an average speed zone should normally be blank.

What if the signs at roadworks disagree?

If you are unsure which limit applies, follow the lower one. National Highways gives exactly this advice, and it is the calm choice in narrow lanes with people working close by.

What are typical limits through roadworks?

The limits vary by scheme. In 2026 the A9 works between Tay Crossing and Ballinluig had a 40 mph limit and the A66 between M6 junction 40 and Temple Sowerby had a 40 mph limit, while National Highways refers to 50 mph limits around motorway roadworks. Always go by the signs in front of you.

Where are average speed cameras in the UK?

Average speed cameras are found on permanent routes with a history of collisions and, temporarily, at major roadworks. We found no current national list or count, so we do not quote one here. The table at the top of this article gives examples from 2026.

Are there average speed cameras on the A9?

Yes, Police Scotland lists the A9 from Perth to Inverness as a permanent average speed system, alongside the A90 from Dundee to Stonehaven. When Transport Scotland announced the A9 system in 2013, it was planned to cover about 136 miles from Dunblane to Inverness.

Which was the first average speed system in Scotland?

Transport Scotland says the first was on the A77 in Ayrshire, installed in 2005.

Can average speed cameras appear on remote roads?

Yes. In September 2026 temporary cameras began operating on the A82 at Glencoe and the A85 between Tyndrum and Dalmally. Police Scotland says they run on solar power, so they can be placed in remote spots without fixed infrastructure.

Do average speed cameras reduce collisions?

Yes, the evidence points to fewer serious collisions on the roads where they are used. Road Safety GB reported in October 2016 on RAC Foundation research that found these results:

• Fatal and serious collisions fell by 36% after average speed cameras were introduced, after allowing for natural variation and overall trends.
• Collisions causing injuries of all severities fell by 16%.
• At the end of 2015, at least 50 stretches of road in Great Britain, totalling 255 miles, were permanently covered.

Scotland reports a similar picture. Transport Scotland linked the A77 system to a 46% drop in fatal accidents and a 35% drop in serious accidents. The idea is simple: steady, similar speeds make for a calmer road. As Superintendent Andy Barclay of Police Scotland put it in September 2026, "Even a small reduction in excessive traffic speeds can deliver improvements to road safety."

What do average speed cameras mean for your next drive?

When you see the yellow cameras or the signs for an average speed section, check the limit, settle at a steady speed at or below it, and hold it to the end of the section. There is no need to watch the cameras themselves. Keep your attention on the lanes, the workers and the traffic around you, and if the signs are unclear, follow the lower limit. It also helps to know your national limits, which our guide to the national speed limit in the UK sets out by road and vehicle.

Ghost helps you get settled in good time. It warns you about known average-speed zones and fixed speed cameras about 700 m ahead and again at 250 m, with one tone and no voice, so you have a calm moment to check your speed. 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. Fewer surprises, and a more relaxed drive home.