Speed camera calibration

ontheroad1970

[Deleted User] said:

I've explained this before. You ideally want two measurements to rely on, but even if you only have one, it's been established that you must have the possibility of challenging the police evidence.

And as we all know, the Home Office is far from infallible.

You can win, but you need strong evidence and a good defence.

In other words, it's a scam and the only safe thing to do is about 10 MPH under the limit, to offset errors in the police equipment.

You also need a very healthy bank balance if it goes wrong.  Unfortunately some here talk about this defence as if it is a slam dunk.  It's far from that, and people should be pragmatic, especially when they qualify for a course.  Remember the guy from Bristol who fought it on principle?  It cost him £75k.  He's not the only example.  

ontheroad1970

maxmycardagain said:

My dashcam saved me, the ticket gave time, date and speed, the dashcam showed i was not yet in the 30, thier camera was detecting into the 60 before the 30 even started and i was doing 36(in the 60) then 28 in the 30....

That's where a dash cam CAN help, but you need the actual money shot to prove it, and you aren't likely to get that until you have turned down the out of court settlements.  Remember that the cameras have a range of 1000m and could get you before you have seen them since they are using very long lenses.

forgotmyname

Car_54 said:

forgotmyname said:

If the ticket said 46mph the actual speed would have been higher. They already deducted a set amount to avoid the cases where its
so close that the calibration comes into it.

Nonsense. If the ticket says 46, then the police must be able to produce evidence that it was 46.

There is a guideline , where no action is taken at speed below 110% of the limit plus 2 mph. That avoids "the  cases where its so close that the calibration comes into it.".

Not rubbish at all,  Calibrated HGV tacho's do not lie.

Driver's received speeding tickets and we could see that the actual vehicles speed was in excess of that put on the speeding ticket.

forgotmyname

Okell said:

forgotmyname said:

If the ticket said 46mph the actual speed would have been higher. They already deducted a set amount to avoid the cases where its
so close that the calibration comes into it.

At least another 2mph if they put 46mph the actual speed would have been at least 48mph.

What?!?!     

One example the driver of a 17ton vehicle which was restricted to 40mph on the road at that particular time received a ticket for 52mph.
The calibrated tacho showed the vehicles true speed to be 56mph.  He was flat out on the speed limiter.

daivid

ElefantEd said:

[Deleted User] said:

Unfortunately, unless you have evidence that you were not speeding, like GPS logs or a dashcam that shows your speedometer, you are screwed.

The court won't care about missing certificates, they will assume the speed camera is infallible. The normal "beyond reasonable doubt" standard doesn't apply in practice.

No, the fact that they don't prosecute until the recorded speed is well over the actual speed limit is how they take into account that the speed camera isn't guaranteed perfect. If they were assuming the camera was infallible they would prosecute at 1mph over the limit. Not doing so until 46mph in a 40 mph limit is giving a very wide margin for error - speeds recorded at between 41 and 45 are given the benefit of reasonable doubt.

10% +2mph is a political/pragmatic decision to do with the idea of not wanting to have eyes glued to speedos and avoiding complete alienation of the motoring public. If the political will was there to prosecute 1/2 a mph over it would happen. As said already someone who was monitoring their speedo when passing a camera at 46mph is likely to have seen around 50mph displayed, they may accept it's a fair cop but far fewer would if prosecuted for a mph or two over.

ontheroad1970

daivid said:

ElefantEd said:

[Deleted User] said:

Unfortunately, unless you have evidence that you were not speeding, like GPS logs or a dashcam that shows your speedometer, you are screwed.

The court won't care about missing certificates, they will assume the speed camera is infallible. The normal "beyond reasonable doubt" standard doesn't apply in practice.

No, the fact that they don't prosecute until the recorded speed is well over the actual speed limit is how they take into account that the speed camera isn't guaranteed perfect. If they were assuming the camera was infallible they would prosecute at 1mph over the limit. Not doing so until 46mph in a 40 mph limit is giving a very wide margin for error - speeds recorded at between 41 and 45 are given the benefit of reasonable doubt.

10% +2mph is a political/pragmatic decision to do with the idea of not wanting to have eyes glued to speedos and avoiding complete alienation of the motoring public. If the political will was there to prosecute 1/2 a mph over it would happen. As said already someone who was monitoring their speedo when passing a camera at 46mph is likely to have seen around 50mph displayed, they may accept it's a fair cop but far fewer would if prosecuted for a mph or two over.

On Public Holidays in New Zealand, as well as restaurants charging a surcharge (often 15%), the tolerance for speed is reduced from 10% to 1km/hr.

[Deleted User]

TooManyPoints said:

it's been established that you must have the possibility of challenging the police evidence.

I don't think anybody is arguing about that. That possibility is provided when the defendant goes to court. What is important is that the defendant understands where the "burden of proof" lies. The police do not have to prove that their device is reliable. The defendant has to cast doubt on its reliability. That doubt does not have to be beyond any doubt at all; it has to be beyond "reasonable doubt". A court may find that it is reasonable to doubt that an unapproved and uncalibrated satnav, operated by somebody who was driving at the time, was more reliable than a Home Office approved device operated correctly.

They might find that, which is why I suggest two forms of measurement to help tip the balance.

Unfortunately it is fundamentally unfair, because the cameras are demonstrably fallible. What's more, GPS is extremely reliable, more so than the cameras for speed over a number of seconds. The receiver doesn't require calibration either.

The system is flawed and not in your favour. Hence my recommendation to do at least 10 MPH under the limit where there are cameras, or just all the time.

[Deleted User]

ontheroad1970 said:

maxmycardagain said:

My dashcam saved me, the ticket gave time, date and speed, the dashcam showed i was not yet in the 30, thier camera was detecting into the 60 before the 30 even started and i was doing 36(in the 60) then 28 in the 30....

That's where a dash cam CAN help, but you need the actual money shot to prove it, and you aren't likely to get that until you have turned down the out of court settlements.  Remember that the cameras have a range of 1000m and could get you before you have seen them since they are using very long lenses.

There is no way those cameras can be accurate at 1000m. Lasers diverge too much, and the simple radars in fixed ones diverge and can't discriminate at that range.

Additionally, tiny vibrations at the camera as vehicles go past are multiplied with distance, and at 1km would be randomly targeting things in that general direction, not a specific car.

WellKnownSid

[Deleted User] said:

ontheroad1970 said:

maxmycardagain said:

My dashcam saved me, the ticket gave time, date and speed, the dashcam showed i was not yet in the 30, thier camera was detecting into the 60 before the 30 even started and i was doing 36(in the 60) then 28 in the 30....

That's where a dash cam CAN help, but you need the actual money shot to prove it, and you aren't likely to get that until you have turned down the out of court settlements.  Remember that the cameras have a range of 1000m and could get you before you have seen them since they are using very long lenses.

There is no way those cameras can be accurate at 1000m. Lasers diverge too much, and the simple radars in fixed ones diverge and can't discriminate at that range.

Additionally, tiny vibrations at the camera as vehicles go past are multiplied with distance, and at 1km would be randomly targeting things in that general direction, not a specific car.

We don’t trust ToF optics a mile down the road yet we put our trust in a weak radio signal from a random spacecraft 12,000 miles away? 😄

Herzlos

[Deleted User] said:

Unfortunately it is fundamentally unfair, because the cameras are demonstrably fallible. What's more, GPS is extremely reliable, more so than the cameras for speed over a number of seconds. The receiver doesn't require calibration either.

If the cameras were demonstrably fallible, you can presumably demonstrate the failure?

Lazers are incredibly accurate at any length as they are largely unaffected by external conditions, can have very precise wavelengths and timings. It's in the millisecond range so very little scope for inaccuracy. 

GPS isn't that accurate because it's triangulating between satellites, doesn't have any real awareness of the local geography, and can easily be skewed by obstacles. Have you never seen your car on a GPS jump onto an adjacent road, a field, change direction or anything? It's happened with my car and bicycle and seems more prominent on the bicycle because the route is logged and the trace line can be pretty erratic.

GPS is accurate to about 4-5m which is fine for navigation but gives a huge margin of error when trying to figure out an instantaneous speed.

Lasers are accurate to sub-mm level which means the instantaneous speed is accurate well beyond any meaningful debate. Was the car going at 46.877mph or 46.878mph? Who cares.