Can dashcam evidence be used for speeding offences?

[johncrossley]

Some drivers overtake other drivers who are already doing the limit, which means they cannot use the excuse that they didn't realise they were accidentally going over the limit. Can dashcam evidence be used here?

 

[GusB]

Some drivers overtake other drivers who are already doing the limit, which means they cannot use the excuse that they didn't realise they were accidentally going over the limit. Can dashcam evidence be used here?

Commercial dashcams won't be calibrated in the same way as those used by the police (if they actually record speed at all), so I very much doubt that they could be used as evidence of speeding.

 

[johncrossley]

Commercial dashcams won't be calibrated in the same way as those used by the police (if they actually record speed at all), so I very much doubt that they could be used as evidence of speeding.

The time taken can be calculated by recording the time landmarks at the side of the road were passed. Modern computer technology is clever enough to work out the speed just by looking at video footage. Compared to other things artificial intelligence is already doing this is quite simple. Obviously you would have to allow a greater tolerance compared to police equipment. But if the driver is clearly way over the limit (for example 45 mph in a 30 mph limit) then there won't be any doubt.

 

[61653 HTAFC]

Do you mean the dashcam footage of the overtaking vehicle, or the one being overtaken?

Most police forces have a team where you can send dashcam clips to report driving offences you've captured, but you'd be rather silly to self-report in that manner. It's also worth noting that speedometers tend to under-read by at least a few MPH so the GPS-based speed on your dashcam (if you have it displayed on the footage in your settings) will probably be more accurate. So if you're driving at an indicated 70mph on your speedo and someone overtakes, they aren't necessarily speeding themselves.

 

[90019]

Can dashcam evidence be used here?

No.

They can be used to prosecute for offences like careless or dangerous driving, which excessive speed can fall under, but can't be used as evidence for a speeding offence due to lack of calibration and inability to prove exact speeds.

 

[AlterEgo]

The time taken can be calculated by recording the time landmarks at the side of the road were passed.

Not from some random person's video footage it can't, because it isn't calibrated and might not even play at the correct speed.

 

[johncrossley]

Do you mean the dashcam footage of the overtaking vehicle, or the one being overtaken?

Footage taken from the vehicle being overtaken. It is naturally of great frustration to obey the speed limit when someone else overtakes at a much greater speed. In this case the driver cannot use the excuse that he didn't know what speed he was doing. Speed cameras are only in a very small number of locations and relying on police patrols is of course not economically viable. Therefore additional recordings are necessary to properly enforce speed limits. Modern technology should be able to use dashcam footage intelligently, and should be able to work out whether the footage is genuine. Traditional calibration shouldn't be necessary as it should be able to intelligently adjust footage as necessary.

 

[61653 HTAFC]

Footage taken from the vehicle being overtaken. It is naturally of great frustration to obey the speed limit when someone else overtakes at a much greater speed. In this case the driver cannot use the excuse that he didn't know what speed he was doing. Speed cameras are only in a very small number of locations and relying on police patrols is of course not economically viable. Therefore additional recordings are necessary to properly enforce speed limits. Modern technology should be able to use dashcam footage intelligently, and should be able to work out whether the footage is genuine. Traditional calibration shouldn't be necessary as it should be able to intelligently adjust footage as necessary.

To be fair the "excuse" that a driver didn't know what speed they were doing is never a valid defence. It's the responsibility of drivers to monitor their own speed and the speed limit of the road they're driving on.
Personally if I'm driving at or near the speed limit and someone overtakes me, they aren't hindering my progress at all so I'm not overly bothered by it. If they're driving in an aggressive or dangerous manner I'd rather they be ahead of me than tailgating for example. It only affects me if they crash a short distance ahead and end up blocking the road. Obviously I'd rather everyone drove safely and within the bounds of the law, but I can't control what others do.

If you have a dashcam clip of someone driving in an unsafe and/or illegal manner, you can submit this to the appropriate police force. Most forces will have a portal on their website to do this. Whether anything comes of it will depend on a number of factors from the quality of the footage to how vigilant that particular Police Force is, to which member of staff happens to be examining the submissions on a particular day. All you can do is submit the footage.

 

[JohnMcL7]

No.

They can be used to prosecute for offences like careless or dangerous driving, which excessive speed can fall under, but can't be used as evidence for a speeding offence due to lack of calibration and inability to prove exact speeds.

Agreed, you can see the same often on police programs when they've stopped a car they suspect of speeding you'll see later they were charged with careless or DWDCA because they didn't have enough evidence for speeding.

Footage taken from the vehicle being overtaken. It is naturally of great frustration to obey the speed limit when someone else overtakes at a much greater speed. In this case the driver cannot use the excuse that he didn't know what speed he was doing. Speed cameras are only in a very small number of locations and relying on police patrols is of course not economically viable. Therefore additional recordings are necessary to properly enforce speed limits. Modern technology should be able to use dashcam footage intelligently, and should be able to work out whether the footage is genuine. Traditional calibration shouldn't be necessary as it should be able to intelligently adjust footage as necessary.

The proof standard for speeding is very high and video footage is simply not good enough to meet that standard, there's no magic 'intelligence' wand that can fix that no matter what Sam Altman tells you.

 

[blueberry11]

I would like to point out that if anyone submits footage to the police, they have to follow the relevant policy for their police force (such as 1 minute before and 1 minute after the offence and not publishing the content online (or being told to delete them)). Also, the submitters own driving would likely be taken into account, so that if they also break the rules, they would also be prosecuted.

Also, keep in mind that if a driver is just a few over the limit, any penalties is unlikely as it has to be 10%+2.

 

[styles]

Yes and no.

Strictly speaking, they won't pass as evidence for 'speeding' offences which require at least two forms of evidence from Home Office approved devices, which dashcams aren't. DCS Andy Cox was campaigning for them to be accepted as the frame rate combined with fixed points of reference in the video could be used to calculate speed, but the can got kicked.

However, if somebody in a dashcam video is clearly driving well above the posted limit, then it can be used as evidence in careless driving and dangerous driving cases.

== Doublepost prevention - post automatically merged: 16 Dec 2025 ==

Also, keep in mind that if a driver is just a few over the limit, any penalties is unlikely as it has to be 10%+2.

It doesn't have to be 10%+2mph over. This is NPCC guidance, which individual forces implement as they see fit. Most do follow 10%+2mph thresholds for fixed speed cameras, but may apply a different threshold for e.g. handheld speed cameras, or indeed dashcam footage. In Police Scotland territory, I've known a family member done doing 76mph on an unrestricted motorway, so that wasn't even 10% over, let alone 10%+2mph over. He still speeds, so hasn't learned his lesson, especially silly as Scotland don't offer speed awareness courses, but oh well. Police Scotland don't publicly disclose their speed enforcement thresholds for what it's worth. The Met used to operate 10%+3mph but a few years ago dropped to 10%+2mph to standardise a bit.

== Doublepost prevention - post automatically merged: 16 Dec 2025 ==

To be fair the "excuse" that a driver didn't know what speed they were doing is never a valid defence. It's the responsibility of drivers to monitor their own speed and the speed limit of the road they're driving on.

Indeed. And speedometers in cars can overestimate the true speed by a massive 10%+6.25mph by law. In practice, older cars are more likely overestimating by about 5mph at 70mph, and newer cars maybe 1-2mph. Either way, no car is 100% accurate and as they are legally not allowed to underestimate speed, they all have at least some margin of overestimating, so somebody caught speeding will have seen an even higher speed reading on their speedo than they were actually doing. Then there's the enforcement thresholds (usually 10%+2mph but it does vary). Then in England, Wales, and Northern Ireland, a speed awareness courses is usually (again, guidance) offered up to 10%+9mph above the limit. Not to mention that fixed position speed cameras are mostly bright yellow or yellow/red stripes (Home Office guidance), mobile speed cameras are often quite visible, both are reported on Google Maps, Waze, etc.

I have little sympathy for people who manage to get points on their licence for speeding as they're either driving well above the posted limit, or are habitually speeding and getting caught; and in both cases be inattentive to not spot the cameras. Getting done once, a bit daft; getting done multiple times, idiotic.

 

[jfollows]

However, dash cameras have been used to identify failings in large numbers of speed cameras, https://www.dailymail.co.uk/news/ar...gly-fined-speed-camera-scandal-motorways.html

The malfunction only emerged after motorists were able to show the courts dashcam footage proving their vehicle was travelling below the speed limit when they were caught.

The issue appears to be that when a variable speed limit increases, and so drivers speed up, the cameras continue to enforce the previous, lower limit for ten seconds.

Tens of thousands of case cancellations and convictions going back four years need examination. Presumably there was a lot of “our systems are infallible” until the weight of evidence to the contrary became unavoidable.

Better: https://www.theguardian.com/money/2...ines-could-be-cancelled-after-technical-issue

Thousands of speeding fines could be cancelled after a “technical issue” triggered some speed cameras in England to incorrectly penalise motorists.

National Highways has apologised for the error, which meant a “very small number” of drivers had been wrongly fined since 2021.


A software update is thought to have created a problem with variable speed cameras on some A-roads and motorways, meaning drivers were incorrectly detected as speeding after the limit had increased.

The minimum penalty for speeding is a £100 fine and three penalty points.


The National Highways chief executive, Nick Harris, said: “Safety is our number one priority and we have developed a fix for this technical anomaly to maintain the highest levels of safety on these roads and make sure no one is wrongly prosecuted.”

National Highways said it had identified about 2,650 incorrect camera activations since 2021, less than two a day, and amounting to less than 0.1% of the 6m activations in the same period.

The issue affected 10% of motorways and A-roads in England, and the agency is working to implement a solution to the problem as soon as possible.

Anyone who has been incorrectly fined will be contacted directly by the police, with fines reimbursed and any points removed from their licence.

Police forces have temporarily stopped issuing fines from variable cameras until they have confidence nobody will be wrongly prosecuted.

A spokesperson for the Department for Transport said: “We apologise to anyone who has been affected. Safety was never compromised, and we are working with policing to ensure nobody is incorrectly prosecuted in future.

“Enforcement is still in place, and the public can remain confident that only motorists who break the rules will be penalised.”

A spokesperson for the National Police Chiefs’ Council said police forces were working to identify and contact “a very limited number of motorists”.

They added: “Policing enforces a range of offences, including speeding, on the strategic road network through a number of tactics including mobile camera deployments, roads policing patrols and average speed sites.

“This remains unchanged. If you are affected by this issue, you will be contacted and details of the compensation scheme will be shared in due course.”

 

[styles]

However, dash cameras have been used to identify failings in large numbers of speed cameras, https://www.dailymail.co.uk/news/ar...gly-fined-speed-camera-scandal-motorways.html

The issue appears to be that when a variable speed limit increases, and so drivers speed up, the cameras continue to enforce the previous, lower limit for ten seconds.

Tens of thousands of case cancellations and convictions going back four years need examination. Presumably there was a lot of “our systems are infallible” until the weight of evidence to the contrary became unavoidable.

Better: https://www.theguardian.com/money/2...ines-could-be-cancelled-after-technical-issue

I read that this morning. Doesn't surprise me this sort of error would eventually occur with the (in)competency of National Highways.

They are however right to point out that this will only have affected 2 drivers a day, or 0.04% of activations, and they'll thankfully be reimbursed and have points scrubbed. I wonder how they're dealing with people who did speed awareness courses as a result of the cameras triggering.

 

[jfollows]

It’s also indicative of how software errors affect normal lives these days. I’ve worked since 1980 in “IT” but back then we consoled ourselves that nobody died because of software errors. That’s no longer true, although of course not in this particular case. I don’t believe that software quality has improved since back then either.

 

[johncrossley]

Do other countries accept dashcam evidence for speeding?

Are there any countries or parts of country where speeding is considered antisocial behaviour and so hardly anyone does it?

 

[jfollows]

I read that this morning. Doesn't surprise me this sort of error would eventually occur with the (in)competency of National Highways.

They are however right to point out that this will only have affected 2 drivers a day, or 0.04% of activations, and they'll thankfully be reimbursed and have points scrubbed. I wonder how they're dealing with people who did speed awareness courses as a result of the cameras triggering.

I imagine the course fees will be reimbursed. Not the time spent taking the course plus holidays taken I guess.
More importantly, I suggest, are the people with unwarranted higher insurance premiums since being incorrectly convicted. Will they be able to claim this money as well?

 

[Tetchytyke]

The presumption in law is that a computer system is accurate unless it can be proven by the defendant that the computer system is not accurate. The burden of proof is on the defendant to prove that the system is faulty, not on the prosecution to prove that it was operating correctly.

We should just file this as yet another example of why this presumption in law is wrong and facilitates miscarriages of justice.

They are however right to point out that this will only have affected 2 drivers a day, or 0.04% of activations

But last week they'll have been saying that the cameras were fine, nothing wrong at all with them, and prosecuting on that basis. But now the cameras weren't fine but it's only a small number of people affected.

I'm not entirely sure I'd believe their protests that it's only a small number of people affected.

 

[renegademaster]

The time taken can be calculated by recording the time landmarks at the side of the road were passed. Modern computer technology is clever enough to work out the speed just by looking at video footage. Compared to other things artificial intelligence is already doing this is quite simple. Obviously you would have to allow a greater tolerance compared to police equipment. But if the driver is clearly way over the limit (for example 45 mph in a 30 mph limit) then there won't be any doubt.

You'd have no way of proving the frame rate

 

[125Spotter]

The presumption in law is that a computer system is accurate unless it can be proven by the defendant that the computer system is not accurate. The burden of proof is on the defendant to prove that the system is faulty, not on the prosecution to prove that it was operating correctly.

We should just file this as yet another example of why this presumption in law is wrong and facilitates miscarriages of justice.

Honestly, it's shocking that this is or ever has been the case – particularly when considering the (a) asymmetric information problem that the accused likely has in this context – they likely won't ever have sight of the actual source code or have the technical knowledge to understand how it actually works to defend themselves, and (b) you've implied this but no matter how good the specification, we know in practice that all systems have unintentional defects or corners cut in the interests of quick delivery.

The forthcoming disaster where more code is written by "AI" is only going to test this position to its limits. My sympathies go to all of the drivers involved who were wrongly accused.

 

[styles]

The presumption in law is that a computer system is accurate unless it can be proven by the defendant that the computer system is not accurate. The burden of proof is on the defendant to prove that the system is faulty, not on the prosecution to prove that it was operating correctly.

This isn't strictly the presumption in law though. Speed measurement devices used for prosecuting speeding offences must be Home Office type approved; they don't just accept any device. The accuracy of it can be challenged in court and calibration certificates and records demanded. It is of course unacceptable that this issue has happened with some sort of limit change timestamping and perhaps the Home Office type approval requirements will change to account for this. But I think it's a far cry from saying computer systems are presumed accurate - there's a fair number of checks and balances.

We should just file this as yet another example of why this presumption in law is wrong and facilitates miscarriages of justice.

Well, mistakes in the legal system are inevitable. The duty of the legislature and the judiciary is to minimise the risk of this as far as practicably possible. I would say that fixing driving records, turning the cameras off, and undertaking a review of what has led to this and how it can be prevented again is pretty reasonable. The alternative is to presumably just to remove all speed cameras, CCTV, noise level detectors, anything with a microchip because the software or the hardware can never be infallible.

But last week they'll have been saying that the cameras were fine, nothing wrong at all with them, and prosecuting on that basis. But now the cameras weren't fine but it's only a small number of people affected.

I'm not entirely sure I'd believe their protests that it's only a small number of people affected.

I actually suspect the number of people affected beyond £100 plus a speed awareness course (typically offered up to 10%+9mph over the limit, very generous) or 3 points (which on its own doesn't bump insurance premiums significantly) will be minimal.

I do think people are sometimes too trusting of what a computer spits out, but I don't really think this is an egregious example of that.

My usual advice stands on this mind - get a dashcam. I've never had an invalid (or a valid!) speeding ticket, but if I did get one, I'd have dashcam footage of the speed limit being X and me travelling roughly at X, not Y.