Safe Speed Forums

Pocket GPS World - Here
Or better yet withdrawn period, and a serious concentration on proper and intelligent road safety restored !

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

If the application of the law was just, and absent other factors that made this particular unit uniquely defective, this should be enough to satisfy reasonable doubt in any other case involving the same model of equipment.

Given my experience of magistrates, I bet it isn't though.

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Regulation without education merely creates more criminals.

There is more to comparing vehicle tracking records to speed camera values. What period was the average speed taken over for instance. The majority of vehicle tracking systems like the one in the article have periods of spot data of 5 minute intervals while the speed camera takes the speed in a very short time. It is likely that the driver will have slowed down or braked at the camera, even though it was too late in this example, so reducing the average speed when taken over a longer period than the camera measured the speed of the vehicle. The magistrates and the court clerk are not qualified to compare the data they were presented with, neither is the van driver or the Navman supplier of it so it should have been presented to someone who could make that comparison for the court. The legal and technical process has not been correctly followed in this case and the chap is therefore lucky to have been acquitted, that acquittal being in my opinion wrong.
I don't believe that the camera was incorrect on the strength of the evidence adduced from a vehicle tracking system as the sampling rate is insufficient for comparison. There is also no mention of a witness from Navman attending court so the evidence, if presented by the defendant is, as I understand it hearsay.
Don't get too excited, the camera has not been proved to be incorrect on this occasion.

Really?
If so, are they also not qualified to understand things like slip-effect?


I agree. However, the actual sampling rate of this particular system will have to be determined, as well as any maximum and minimum values within a sample group (should they exist).

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

A lot of people who speak of it have very little understanding of it at all. No I doubt very much if many Magistrates have an understanding of it but of course some will be qualified to appreciate the difference between someone who tells them how it does or doesn't work as opposed to someone who is spouting bovine excrement on the subject.


All of the vehicle tracking systems evidence I have seen is insufficient to be used as evidence in a speeding case. The stored vehicle position and average speed being sampled over several minutes rather than several times a second. When you consider the data required to be transferred and stored to achieve the required rate for comparison then the tracking system would no longer be commercially viable perhaps.
The speed cameras are not time-synchronised either so the data is not particularly valid unless a constant speed can be verified with a high enough sampling rate.
Vehicle tachographs are not particularly useful for the same reasons. If a slow speed is coincident with the speed camera speed on a tachograph then coincidentally the speed camera speed will most likely be present either side of the exact time. I have seen a petrol receipt from a motorway service station served in evidence of an average speed, this was just as valid as the GPS data in the case mentioned, until speed cameras are time synchronised to motorway service station tills the data is worthless as, in my opinion, is vehicle tracking data such as that used here. The till receipt showed the vehicle would have to be driven at 180mph to get to the speed camera location but the offence was 90mph or so...so what? 2 clocks, 2 different times, evidence worthless.
A funny story for you. A truck driver submitted a tachograph that showed him stopped in a goods yard at the time of an offence of 41 in a 30mph sped limit. Either side of the time in the goods yard were speeds matching 41mph. The clocks were not synchronised. Tachographs have to have the start and end locations written onto them and when this was examined it showed that for more than 100 miles on that tachograph the vehicle was driven at 56mph in a 40mph speed limit. When this was presented to the driver his response was "I always drive at 56 in a 40, everyone does!". It's not funny when your operating licence goes at the same time as your driving licence...but that depends who you are I suppose.

What kind of an answer was that?
Are they not qualified (hence not qualified to understand slip-effect), or are some qualified?


Have you seen all of them? Do you know the "Navman Wireless" system?
Of course you can speculate, but we shouldn't jump to conclusions based on mere assumptions.


That's not needed when also recording the maximum and minimum.

So is there no possibility of storing "maximum and minimum values within a sample group"?


They need not be.
It is known where the camera is (I hope); we know where the vehicle was within reason. Any time differential can be reasonably deduced.


Before you continue:
I have already agreed with you that the evidence as reported is not enough to show the camera was incorrect.
I'm merely pointing out to you that evidence we don't know of that could reasonably exist may actually prove the error.
We need to determine the facts about this particular system.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

and I quote :
Pocket GPS World - Here
That looks like a witness from Navman to me. I agree there is little mention in this report about how accurate the system is but there was a case in the States that proved their speed in this way and won.

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

Surely the evidence of the Trackman is sufficient to establish reasonable doubt in the mind of the Magistrate. And, believe it or not Greenshed, the law pertaining to speed cameras is no different to the great corpus of British law when it comes to reasonable doubt.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

I'll give you that the Navman chap was there, so not hearsay.

I still don't accept that the data would have been sufficient to show doubt if there was an expert witness to reply which it seems there was not.

Here's what the system reports, speeds are average for the period:


It appears that the shortest report period is 1min. I downloaded the software and that was the shortest period I could input. This is insufficient for the comparison to be made against a speed camera in my opinion.
Unless the Navman chap had access to data that was saved at a greater rate than that of the reporting software then the comparison is invalid.
There is an overspeed indicator but that is configurable so it can be switched off. I have seen some company vans that I understand are on these or similar trackers and they either have overspeed switched off or are constantly raising alarms and ignoring them.
No data sampling at a rate of at least 4/sec and lack of maximum speeds in each reporting line and you may as well throw it away or of course rent someone to say, unopposed how it compares to a speed reading taken over a maximum of 1/3rd or 4/10ths of a second.
It would be interesting to see the report.
I am aware that the cases need to be proven to reasonable doubt but do not agree that unopposed doubt is in any way reasonable; perhaps they should have adjourned for the defence report to be examined.

You can instil doubt in a magistrate's mind very easily when you have the credentials to do so and present the information unopposed and when the expert witness most probably has no understanding of the system he is comparing his evidence with. In that respect I would say that doubt is not at all reasonable.
The Crown should have requested and have been given an adjournment to reply or the evidence not be admitted if not served in time.
I have downloaded the admin software for the system from the vendor and see that the reports within it and log facility are not sufficient as I suggested above. I have seen these before and they are not adequate evidence to dispute a speed camera evidence.
The only way that the evidence could have been useful is if the chap had recovered the data from the unit in the vehicle and that data was sampled and saved at a rate fast enough to make it comparable. I have doubts (quite reasonable in my opinion) about whether data was recoverable from the unit or that the unit samples quickly enough to make a comparison. Typical sample rates of vehicle navigation systems are 1 to 4 seconds/sample. Fast sampling and storage GPS systems are relatively expensive; I use systems that sample at 20Hz and at 100Hz and they are in the region of £3k to £4k per unit respectively. Do you really think Navman are supplying this sort of unit and transferring that volume of data via Vodaphone? I don't think they are not I know they will not be unless the vehicles being tracked are dealing in cocaine and have ready made custom with large bags of cash.
I think my evidence and experience of these matters is stacking in my favour; happy to read the alternative implementation from you and start my own commercially viable vehicle tracking/anti speed camera evidence business.

You know, I really think you should do just that.
Think about it - from what you've said here, most people who have the misfortune to be wrongly accused of speeding really don't have a leg to stand on. They have virtually no defence which would stand up in court, so no matter how aggrieved they are, they have little or no option but to pay up and accept the points.
There's where you can help - many people whose livelihoods are on the line would probably be more than happy to fork out a few quid to someone who could give them a fighting chance of proving their innocence. And your experience in these matters would be invaluable.
Over to you then, I can't wait to see your business cards.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

I can only assume you agree that provides enough resolution to ascertain travelling speeds, especially significant deviations from the limit above the prosecution threshold.


That would of course be quite silly. The "1 to 4 seconds/sample" for today's speed displaying sat navs is plenty.
If that data is required, techniques such as time compression can be used to 'squeeze' data spanning a significant time (the 1 minute or whatever) into a short data packet, rather like a mobile phone transmission. Lossless compression will take care of the rest.
An even better approach would use an 'event driven' system, noting only events of significance, so not broadcasting/storing data of insignificance - hence no "volume of data".
Could this be how the 'overspeed' indicator works?


Perhaps it was left on in this case?


Please can you state how you confidently know that?
Were the company vans that you say were "constantly raising alarms" were also "dealing in cocaine and have ready made custom with large bags of cash." ? If not, then haven't you just contradicted yourself?

I agree GPS speed displays can give bum readings in certain conditions, but it is a bit more difficult to hide elevated readings within an otherwise unchanging data set with a device that measures distances - especially where the signal integrity is apparently so good (locked on to 8 satellites).
We also know the LTI can also give bum readings in certain conditions....


Your "favour"? What an interesting sentiment!

Thus far, 'evidence and experience' suggests you make too many assumptions.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

So are you trying to say that if he exceeded the speed limit it would have been within a maximum four second timescale and then decelerated to within the limits within the sam 4 seconds max? If this is this case and he was exceeding the limits by accelerating and decelerating within such a short time scale...IS IT REALLY SUCH A SERIOUSLY LONG TIME SCALE, THAT IS WORTH PROSECUTING ANYWAY?

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

Let me ( and others) get this right GS --

If some CPS BLOKIE does the above ,it's called justice being served .But if someone like Mr Loophole does it- it's called cheating the system ./finding a loophole -most UNBRITISH -like being GUILTY UNTIL FOUND INNOCENT ,as the S(omewhat )C(rafty ) R(ats) would like ALL British motorist to be . ( I used rats ,as they like to sit back and mop up the residue ,and also like some of the SCP , ARE excellent underwater )

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Did you mean S(omewhat ) C(rafty ) P(rats)

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I possibly did - thought the term "Rat"( as n the old saying -"you dirty Rat " was nearer the truth)

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Quoted for truth, please remember that you said this when it comes back to bite you in the proverbial.

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Regulation without education merely creates more criminals.

Please enlighten us as to the requirement for this sample rate, and how it is provided given the current state of satellite positioning technology and accuracy. Bear in mind that my specialist "industry" is at the bleeding edge of this technology, so I will not fail to spot any bolleaux!

(To others, please forgive my multiple posts in quick succession. It is to facilitate quick reference when GS predictably dodges the truths he finds uncomfortable.)

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Regulation without education merely creates more criminals.

I know that there are people here with the expertise, time, and interest to calculate the following:

Given the detection zone of varying scam methods (I am unaware of which one was used in this case), and given that the accused had no knowledge of the sample rate and interval, nor perhaps the lizard-like reflexes to respond to it, and in the knowledge of the typical acceleration/deceleration rates of modern vans; assuming best-case scenario for the van driver, that he was pinged at the start of a 4 second (as cited by Greenshed) interval at 61mph, at what rate, and to what speed, would he have to decelerate in order for the 4 second resolution of the GPS to indicate 48mph?

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Regulation without education merely creates more criminals.

Greenshed, if the CPS believe that the magistrates have made an error in this case, then they are free to appeal to a higher court. Have they done so, or indicated that they intend to do so, in this case?

Do you, as always, think you know better?

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Regulation without education merely creates more criminals.