UK Police speed camera tolerances explained

As you may have noticed, there’s a network of nearly 3250 speed cameras in position on UK roads. While they all enforce the same speed limits, it’s worth remembering that different counties have different rules and tolerances when it comes to how those limits are enforced.

A large portion of the country’s cameras work to a tolerance of ten per cent of the speed limit plus 2mph, including the Metropolitan Police in London and its surrounding areas as of 2019. Previous to this, the Met Police worked to a more generous 3mph margin due to ‘traffic density’ across the London area. It appears that this reduction in the leeway afforded to drivers in London has already caught many people out, but even with the 1mph reduction in tolerance, there’s still a substantial margin for error. 

It’s worth noting that you could still be fined and receive points on your licence for travelling even 1mph over the speed limit. What we’re talking about here are the speed camera tolerances that are employed by individual police forces. In addition, your car’s speedometer is not legally allowed to under-read, so you should never be travelling faster than your displayed speed. Most manufacturers instead over-read by around 3mph in general, giving driver’s even more margin for error against speed limits. 

As reported by our sister title Auto Express, speedometers in modern cars have become more accurate over the years, with some manufacturers actually reading near-accurate when compared to GPS-verified speeds, but with the almost total use of digital speed readouts in many modern cars, keeping an eye on your speed has never been easier. 

Combined with a speeding camera’s built in tolerances, there’s still a wide margin for error on approach as, for example, a 40mph zone camera won’t book you unless you’re going over 46mph, not including the car’s built-in over-read of your actual speed. 

> UK speeding fines 2022: what are the latest penalties?

However, it is still critical to take note of new or revised posted speed limits as they continue to change across the country. Many parts of central London are now limited to 20mph, including large proportions of Westminster and Kensington and Chelsea. Outside of London, smaller cities like Oxford and Cambridge are also switching to 20mph posted speed limits within town centres.

UK speed camera tolerances by police force

Below is a breakdown of the tolerances of various counties across the UK, confirmed under a Freedom of Information request by Auto Express in 2019. We have updated the Met Police entry to reflect its more recent tolerance change to 10% + 2mph