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chopperovski
I have done a search and don't think this has been dealt with before.

I received an NIP stating that the driver of my car had allegedly "exceeded a Local Traffic Order - automatic camera device" AND

"The speed limit for the vehicle was 40mph. The recorded speed was 46mph"

Although it doesn't state as much there are at least 2 average speed cameras so the alleged offence is for average speed.

What is interesting is that the location given is

"M32 , Severn Bridge rail line overbridge to end of M32 southbound, Bristol"

This is a very short stretch of road - approx 800m if one literally took the distance between the rail line overbridge and the end of the M32.

I believe it is possible that there are more than two cameras and that if so the speed may have been measured by a pair that were much less than 800m apart.

The point to my question - is there a minimum distance for measurement - is that I am fairly sure that I did slow down for this stretch and if a very short measurement distance was used then a discrepancy in measurement technique may lead to a false reading.

There are no time or speed stamps on the photos on Avon and Somerset website and when I asked for the camera locations today the operative said she was unfamiliar with the area.



BaggieBoy
Pocket GPS World only has these two camera locations noted, so not very likely extra cameras are involved. 800m seems a responsible distance to be using to me, not aware of a minimum however.
chopperovski
Thanks for the reply.

Do you mean that the cameras are precisely at the rail bridge overpass and at the end of the M32 - which incidentally is at J3 where the M32 becomes the A4032

BaggieBoy
Police using manual time/distance equipment must measure using a distance in excess of 1/8 mile (around 225m). So 800m using likely more precise distance and time values doesn't seem unreasonable.

QUOTE (chopperovski @ Mon, 11 Dec 2017 - 18:05) *
Do you mean that the cameras are precisely at the rail bridge overpass and at the end of the M32 - which incidentally is at J3 where the M32 becomes the A4032


Not sure of the exact locations but PGSWorld has them at that rough positions.
chopperovski
OK cheers. I might need to go and take a look.
Logician
By my calculations the discrepancy in measurement would have to be of the order of 120 metres for 40 mph to be measured as 46 mph over a 800 metre distance, which seems very unlikely. For a successful defence you would need to show not that there was a possibility of an error in the measurement, but that such an error actually occurred.
chopperovski
Yes true - but I would actually only need to get down to 45mph because Avon and Somerset operates a 10% + mph rule so that 45mph wouldn't mean an NIP.

I know that doesn't really help over 800m but if the distance was shorter it might.

Incidentally I note from a FOI that around 9500 motorists caught in a 6 week period this year
southpaw82
No, you’d need to get it down to 40, as any speed in excess of the limit is an offence regardless of whether it’s normally prosecuted or not (unless you want a potentially very expensive fight over the decision to continue a prosecution at less than the normal threshold on public law grounds).
cp8759
QUOTE (Logician @ Mon, 11 Dec 2017 - 18:27) *
By my calculations the discrepancy in measurement would have to be of the order of 120 metres for 40 mph to be measured as 46 mph over a 800 metre distance, which seems very unlikely. For a successful defence you would need to show not that there was a possibility of an error in the measurement, but that such an error actually occurred.

I think that's taking it too far, the OP doesn't need to show that he is innocent. He needs to put forward a reasonable explanation which is consistent with innocence, so as to cast a reasonable doubt as to whether he is guilty. If the court reasonably thinks that he might be innocent, the court is bound to acquit.
Having said that, I very much doubt there's any chance of the distance measurement being off by any material amount

QUOTE (southpaw82 @ Mon, 11 Dec 2017 - 19:06) *
No, you’d need to get it down to 40, as any speed in excess of the limit is an offence regardless of whether it’s normally prosecuted or not (unless you want a potentially very expensive fight over the decision to continue a prosecution at less than the normal threshold on public law grounds).

If he can get it down to 45 or less it would still be worthwhile to ask them politely to drop it, this has been known to happen where a NIP has been issued in error below the threshold for prosecution but above the legal limit. Of course, if he can show the speed was 45 they may well continue, if he shows it's 41 they will probably drop it. However I suspect the odds are it's bang on 46, because a contractor will have been paid quite a few quid to measure that distance exactly.
Jlc
You can bet that the 'exact' distance (give or take 1m) will be known between the pickup points of successive cameras.

QUOTE (cp8759 @ Mon, 11 Dec 2017 - 19:26) *
However I suspect the odds are it's bang on 46, because a contractor will have been paid quite a few quid to measure that distance exactly.

^ This.
chopperovski
Thanks for the replies but this is getting a little off topic.

Avon and Somerset use the APCOA guidlines so I don't think they would issue an NIP @ 45mph

https://www.avonandsomerset.police.uk/14761...ment-guidelines

So my original question about the distance is relevant although clearly not at 800m.

But if the distance was much shorter then a discrepancy in distance, either by measurement, or by the fact that one camera recorded a numberplate at a different distance from it than another could make a vital difference.

As I said I'm pretty sure I'd slowed down so £100 fine plus 3 points is pretty heavy handed in what after all is a motorway.

Just to add a contrast to the earlier figure I quoted, I see from an FOI request to Avon and Somerset that only approx 450 drivers had been done for using mobile phones in the period up to end Sep 2017!
BaggieBoy
Even if you could prove (very unlikely) that your speed was below 46 (but above 40), then you would still be guilty of speeding. To get to this point you would have had to take it to court, and so the court would very likely still impose the same penalty which will see a higher fine and significant costs.
BertB
QUOTE (chopperovski @ Mon, 11 Dec 2017 - 20:28) *
Thanks for the replies but this is getting a little off topic.


Not really. To successfully argue the speed down would require a Newton hearing in court. If you could prove 45mph, while less than ACPO guidelines for the start of prosecution, it would still be admitting exceeding the speed limit by more than 10%, and would attract points, and a fine in excess of the £100 COFP limit. The opportunity of a speed awareness course would also be gone.

However at 41mph you may be able to argue a case should not have been brought. Whether you can do this prior to any hearing in an attempt to convince either the CTO or CPS to drop the case, I do not know. But im sure others will.
Jlc
You would have to show the distance used for the calculation is incorrect. It will have been accurately measured.

Unless you can find out the timestamps and which gantries and measure the difference yourself then you are at a loss.

You can put them to proof but you’ll pay for their expert witness at court if you lose.

The detection point is usually marked by a square dot on the road. Any slight differences in ANPR detection will be all but insignificant unless it was an extremely short distance - which doesn’t apply here.
chopperovski
OK fellas. Many thanks for all the replies. It's nice people take the time.

I think I will go down and have a look and see if I see anything as it was 10pm at night when alleged offence took place.

Maybe I'm clutching at straws here but we'll see.

Will report back if any developments.

Cheers
Logician
QUOTE (cp8759 @ Mon, 11 Dec 2017 - 19:26) *
QUOTE (Logician @ Mon, 11 Dec 2017 - 18:27) *
By my calculations the discrepancy in measurement would have to be of the order of 120 metres for 40 mph to be measured as 46 mph over a 800 metre distance, which seems very unlikely. For a successful defence you would need to show not that there was a possibility of an error in the measurement, but that such an error actually occurred.
I think that's taking it too far, the OP doesn't need to show that he is innocent. He needs to put forward a reasonable explanation which is consistent with innocence, so as to cast a reasonable doubt as to whether he is guilty. If the court reasonably thinks that he might be innocent, the court is bound to acquit.


While that is of course correct as a general proposition, in the case of an approved speed measuring device it is a bit difficult to see how a reasonable explanation can be put forward for it indicating a speed in excess of the limit when the driver claims not to be exceeding the limit, without showing that an error had occurred.

The Rookie
QUOTE (chopperovski @ Mon, 11 Dec 2017 - 23:40) *
I think I will go down and have a look and see if I see anything as it was 10pm at night when alleged offence took place.

Maybe I'm clutching at straws here but we'll see.

Thinking the time is at all relevant is definitely clutching at straws........
cp8759
QUOTE (Logician @ Tue, 12 Dec 2017 - 00:13) *
While that is of course correct as a general proposition, in the case of an approved speed measuring device it is a bit difficult to see how a reasonable explanation can be put forward for it indicating a speed in excess of the limit when the driver claims not to be exceeding the limit, without showing that an error had occurred.

He doesn't need to show that an error actually occurred, he just needs to show that there's a reasonable chance an error might well have occurred
kernow2015
If you really wanted to go at it on a distance angle, you'd have to speak to either Bristol or South Glous Trading Standards who may be able to measure the distance between the markers, but you're then talking costs way in excess of any fine, as you'd be paying for officer time and lane closure, which I just can't see happening.
But someone must have the exact distance written down - we used to assist D&C police with their Vascar markings and approved 20m distance for the LTI gun.
superSmiffy
QUOTE (cp8759 @ Tue, 12 Dec 2017 - 05:30) *
QUOTE (Logician @ Tue, 12 Dec 2017 - 00:13) *
While that is of course correct as a general proposition, in the case of an approved speed measuring device it is a bit difficult to see how a reasonable explanation can be put forward for it indicating a speed in excess of the limit when the driver claims not to be exceeding the limit, without showing that an error had occurred.

He doesn't need to show that an error actually occurred, he just needs to show that there's a reasonable chance an error might well have occurred

How would he make that “reasonable?
The Rookie
The legal point for challenging an approved device comes from R V Skegness magistrates court ex party Cardy
QUOTE
"... the printout is no more than evidence and although, on the principle..., there is a presumption that the device was in order when used, it is open to the defendant to rebut that presumption by calling evidence challenging the reliability of the device at the relevant time."

So there needs to be satisfactory evidence (you could call it proof) casting a reasonable doubt.

In effect its the same as challenging a presumption of service.

For example in Underwood he persuaded the court he could not have been at the relevant gantry (M25 old Gatso cams) at the time in question, so either the NIP was defective (and can you then trust that the 50 limit was displayed) or the speed was displayed at the gantry mentioned and not where Underwood was.
Colin_S
Camera locations here and here?

They look to be a temporary installation for roadworks.
superSmiffy
The minimum distances for average speed cameras are not a secret. Some go down to as little as 75m.

They are still accurate at those short distances.

Where do you plan going with this OP?

QUOTE (Colin_S @ Tue, 12 Dec 2017 - 08:46) *
Camera locations here and here?

They look to be a temporary installation for roadworks.

525m between those. No issues there as far as I can see.
chopperovski
OK a couple of things.

Yes those are not the speed cameras. There were temporary cameras whilst roadworks were being carried out but I believe there are now permanent cameras because there is a bus lane in the outside lane which is for the use of the Bristol Metrobus . The introduction of that bus has been delayed but it appears that the speed restriction remains.

The reason I spoke about time is because over a short distance average speed around the values I am talking about is significantly affected

eg time measured for 225 yds = 10 secs = avg speed 46.02mph

10.25secs = avg speed 44.90mph

Not sure about the comment that says time isn't relevant - average speed between two points is worked out by a calculation involving both time and distance.

Draw your own conclusions but mine is that if the distance was short enough and there was an error in measuring time or distance then the average speed calculation may be wrong.

That's the nub of it really.

I should add that the photos Avon and Somerset allow me to see have no info on them at all - neither date, speed or any other detail.
Jlc
You can 'ignore' time as a variable this is done by synchronised timestamps - this is the easy bit.

The system then calculates the average speed with those timestamps and the provided distance between the cameras.

So, as per your example:

500m in 24.4s = 46mph.

if the actual distance between the cameras was 450m:

450m in 24.4s = 41mph.

So, you just need to find out exactly which gantries were used for this enforcement and the actual distance between them and the presumed distance used. (Of course, if the actual and presumed are the same then there's no issue)
chopperovski
Ok - The part that interests me is that the picture shows the rear of the car so both cameras would have to take a picture at the exact time it was the exact same distance from each camera.In that way the distance between the captured images would replicate the distance between the cameras wouldn't it?

That probably isn't significant over a fairly long distance but could be over a short distance.

I have now been given an email address for the camera unit so I will see what that yields.
The Rookie
Not going to be out by 50metres though is it! :-)
Jlc
QUOTE (The Rookie @ Tue, 12 Dec 2017 - 11:25) *
Not going to be out by 50metres though is it! :-)

Indeed - a metre here or there isn't going to impact the average speed by any significance unless the distance was extremely small. (If they were actually that inaccurate)

But remember the reference point on the road. (That will be the measured distance stored in the system too)

A metre difference from reality for my example above will have less than +/-0.1mph difference.
StationCat
If it was a SPECS camera then the distance is usually measured by RTK corrected GPS surveying - which is accurate to about 20mm. The system uses GPS for its time stamps too so they are effectively perfectly synchronised. There will be a calibration certificate quoting the exact distance between the two points on the road, but the OP probably has to plead guilty and opt for court to get that. Average speed cameras have been operating long enough for the installers to know what they are doing and get it right.
Colin_S
QUOTE (chopperovski @ Tue, 12 Dec 2017 - 11:16) *
Ok - The part that interests me is that the picture shows the rear of the car ........


Are there any marks like the V shape on the road in this speed camera location on the A2 and are they visible in the photos?

These are newly installed and the marks are, I guess, reference marks for calibration or similar.
JC Denton
The minimum distance for most average speed cameras is 100m. But I suspect its rare outside of urban areas for them to be placed that close.

JC
chopperovski
OK brief update and may be of use to anyone driving into Bristol on M32.

Went and had a look at the location of the cameras. They are SPECS3 and each pair is positioned on a yellow pole which is mounted on the concrete central reservation.

Entry cameras about 100m past the railway overbridge and exit cameras just after the overhead roundabout stating motorway ends in 200 yds.

Distance of 532metres between the entry and exit - looks about right on Google maps.

As you probably know the photos you are shown are to assist in IDing the driver and don't give any other detail. Seems you only get that if you challenge it.

Thanks again for all the input
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