Safe Speed Forums

This may not be quite as straight forward as it may seem; it also may not be relevant - it all depends on how the 'overspeed' processing is done.

To follow this through for arguments sake (this is also disregarding acceleration):
assuming a linear deceleration rate (reasonable for brakes), 'start' speed of 61, an 'ave'rage speed of 48; transposing the simple equation (with 'end' speed):
ave = (start+end)/2
2ave = start+end
2ave-start = end = 2*48 - 61 = 35mph.

61mph to 35mph in 4 seconds:
delta = 26mph, per second = 6.5mph/sec = 0.3G.
This rate of slowing is well within reason; however, the prior and subsequent GPS speed readings would be the killer - they would inherently show a huge discontinuity of speed.

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

Cheers Steve! This is of course neglecting human reaction time. I'm also assuming that the speed is measured by a succession of points, rather than Doppler shift, but in the case of the latter, it begs the question, what is GS measuring the speed of that changes so rapidly that it needs sampling one hundred times per second!?

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Regulation without education merely creates more criminals.

i have to say i was also somewhat surprised to hear that the navman evidence was sufficient to stop the prosecution.
i expect a personal GPS log (depending on the form) would be somewhat more open to falsification, so the statement from a 3rd party may have helped.

we're all speculating here on the system setup and the evidence provided, if the judge ruled it sufficient to question the camera reading fair enough. not yet a defence anyone should be gambling their license with.

That's right, just unreliable as evidence in this case.

Interesting that Greenshed clearly believes that the only piece of technology that can accuratley record speed is LTI 20:20 despite all evidence that shows it is deeply flawed.

I don't agree that is what is concluded. What I have said is that the GPS evidence was not examined by an expert for the crown so was unopposed and the GPS experts word taken as given because to the lay person from a technical aspect his story was reasonable.
When the GPS evidence is examined, as similar evidence has been examined in the past, it has been found to be insufficiently representative of the vehicle speed as measured by the camera; i.e. the camera measures a "spot-speed" (a very short distance/time average) and the GPS an "average over a greater time and distance" so it is obvious why there is a difference. Both are showing the correct speed but the speeds do not represent the same speed at the same time. Apologies if that was rambling.

The speed camera has NOT been shown to be unreliable in this case, it has been shown to give the speed of a vehicle. The GPS data has shown the average speed of the same vehicle at a different time period. It is my opinion therefore that the court has been given an incomplete technical argument and has made a decision on what was available to the court in the case presented. The Crown and the court was entitled to apply to have the evidence examined by an expert to comment but chose not to; that does not show the camera was in error on this occasion.


That is what you believe. The "bollix" that has been used as an excuse for tests that show this show exactly what I expect the LTI20:20 to do. The difference between you and I is you see that as a flaw I see it as not causing a problem at all. One of us knows why the other is having a guess; you know who is who.

I also believe it is not a technical difficulty to create a speed meter that measures the speed of a vehicle accurately, reliably and can use physical constants to calibrate itself so it is always correct when used correctly, many do. Why do you believe it to be difficult?

The court dismissed the case because reasonable doubt had been proved on the accuracy of the speedmeter.


If it is not difficult, why are so many flawed pieces of equipment in use? I believe that it is difficult to create a reliable speed gun like the LTI 20:20 because it requires an amateur marksman to aim at a moving target from a large distance. The technology is fine, it is the operator that cannot possibly be relied upon.

Add to that to a van that moves & wobbles every time a vehicle passes it !
Think of how many people you know that can use a camera steadily enough, without any camera-shake and take a 'perfect image' ?

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

What you repeatedly don't seem to get greenshed, is that the camera does not have to be "proven" wrong, the defence only has to establish reasonable doubt. That is the principle of law in this country, innocent until "proven" guilty, not vice versa. There was doubt, and the defendant was given the benefit of that doubt, the court got it right.

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Regulation without education merely creates more criminals.

I have described exactly that; the court has done what you said.

Where we differ is that if the defence expert had been opposed by an equal the decision, IMHO would have been quite different.

In addition what the defence have most definitely not shown is that the camera showed a speed error.

But they have shown that doubt can be cast upon its veracity, which is a step in the right direction.

As you're here, would you care to address any of the points I made earlier in this thread, or any of the myriad of others elsewhere that you have avoided?

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Regulation without education merely creates more criminals.

And that lack of expertise obviously continues within this thread.

How can you dismiss the possibility that the evidence from the GPS supplier was expert and potentially technically correct (see the reasonable possibilities I gave earlier)?


As you rightly said: the issue here is resolution, and it has been shown the resolution potentially can be enough such that the GPS reading could be relied upon.

Fancy addressing my previous post to you? You kinda need to show how that cannot be for you to justify continuing to hold your opinion.


That certainly is a possibility, even likely, but it's not necessarily what actually transpired. It may be that the expert witness demonstrated a complete technical argument. You make too many assumptions - unless you are in a privileged position to know what actually transpired?




Given your total lack of acknowledgement of this post to you, I don't believe you're in a position to pass technical comment on that phenomenon.
I hope you've never used as an expert witness


See my highlight for a hint of the flaw within your argument.

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

The doubt in this case is only there because the doubt cast by the defence expert went unanswered. He could have been commenting on any related subject in a way that would cast doubt if unanswered and because he was a credible and learned (in his GPS system) the doubt he engendered has prevailed. Properly answered he would have not, IMO. have cast any doubt whatsoever on the matter at all.
Are the authorities running back to the test bench to withdraw this camera? They are not because a well known legal tactic has been played upon naive court officials and the GPS evidence used and seen many times before forms no technical challenge to the accuracy of the camera. When comparing chalk and cheese, make sure you eat the cheese and write down what it was like with the chalk. Properly briefed the GPS expert would have, I am certain accepted how his system was not an indicator of the speed of the subject vehicle in the fraction of a second in which it was measured and why.

I don't avoid questions.

It could, however has that been adduced? The typical vehicle tracking system will not retain information at this rate nor does it need to in order to perform its function.


The over speed indicator will be a single event I am sure. I would also say that this would be a reasonable thing for the witness to refer to but we see nothing of that. There would also be the matter of how the operation of that at the time of the offence could be shown to be in order and recorded. We see no mention of it and I would say that would have stuck in the mind of any court reporter.


There are many corporate vehicles being tracked yet are commonly seen in an "over-speed" condition. I'm sure you are familiar with them.

It isn't difficult at all to hide high speed inside of a 1 minute resolution average speed tracking system. This is especially easy when you place a speed enforcement system somewhere on the track of the vehicle during that 1 minute period.


I have made some assumptions, yes but they are based on previous examination of similar data submitted for the same reason. You too have made assumptions but it may be the case that you are basing that on your own feelings and predilection against the speed enforcement system; there you go another assumption but I think you may find it difficult to say it isn't as reasoned as most of yours.

I say again, I have not seen data from this sort of system that would stand against a speed enforcement camera when properly answered. Unless the Navman expert brought data that was significantly more detailed than the normally adduced record sheet the evidence is easily over-turned. If he did bring detailed information that that detailed information should have been thoroughly examined to see if the alleged speed occurred within the data set at a reasonable time either side of the offence time.
GPS data can be compelling to the lay person, as it was in this case but generally, vehicle tracking systems do not provide suitable evidence to show doubt in the accuracy of the type approved speed meter.

Naive court officials? It is not their job to imagine errors in expert testimony, it is their job to assess the evidence in front of them, and they did so correctly in this case. The defence made a point that the prosecution were unable to refute. Merely because it may be possible that the speed was different in between data points does not mean the court have to accept that it was, remember the benefit of the doubt goes to the defendant! Nobody should be punished for possibly exceeding the speed limit for a "fraction of a second" (your words) between data points, especially when adjacent data points show compliance. Are you so bogged down in the technicalities that you have lost the spirit of the law? Do you suppose that he was going around accelerating to illegal speed, and then decelerating in between samples, as if he even had any knowledge of when the samples were being taken, let alone the ability/performance to do so.

What exactly fuels your arrogant attitude that you know better about the company's GPS system than an expert from that company? What are your qualifications and experience? Have you read the court transcripts from this case? I rather suspect you are in possession of very few of the facts, and are defending the speed gun to the hilt due to dogma, rather than intellect. The fact that the authorities are not "running back to the test bench" shows nothing; I'm sure there would be action if this were happening regularly.

You do avoid questions, you have avoided some of mine on this very thread, and many many others elsewhere.

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Regulation without education merely creates more criminals.

Have you seen the evidence from this case?



What indication do you have that it wasn't?



One absolutely did in this case, look at the verdict.

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Regulation without education merely creates more criminals.

Has the lack of been 'adduced'?

To repeat myself:
Such a system need not retain info at that rate (see my earlier "event driven" comment). Do you agree the validity of that method?



How can you be sure of such a thing? Again, see my "event driven" comment.


You may as well have said "It wasn’t reported in the media, therefore it doesn't exist" Come on!


You didn't address my questions.
How do you know the speed function will not be utilised?


It appears you missed my earlier point about 'time compression' - yet you somehow quoted it in another part of your post. Do you actually read my posts at all?
Do you agree than a system can transfer high resolution time data within comparatively infrequent packets?


So why is it in your "favour"?


I don't think so. Can you show where I made these assumptions?


Oooh, verging on ad hominem. Show on other foot: viewtopic.php?p=218616#p218616
So could it be that it is indeed you who is "basing that on your own feelings and predilection for the speed enforcement system" because it is a source of revenue for you? Who has the greater conflict of interest here, huh?


See the link I gave just above. There are plenty more subsequent to that, a quick look around your recent contributions shows you are the biggest evader of all! By all means prove me wrong.
Answer this question!
(reader: watch how well GS doesn't avoid this question)


I have already agreed ("likely"), but "generally" doesn't mean always/automatically/inherently.

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

oh there you go with all of your assumptions again

Do you have any intention of answering any of the questions/points posed to you, that you allegedly do not avoid?

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Regulation without education merely creates more criminals.

Beautiful, so GS in his next post will answer the question:

D'Oh! Maybe not then. Oh well, let's just look back at what it was GS said:

Well technically that is true, he simply doesn't answer them, mainly because he is unable to I suspect.

You haven't responded to my previous post, so I'll put it another way:

What legal defence is there for anyone wrongly accused of speeding? It seems that there is zero, nada, zilch - so if it happens you just meekly pay up.

Putting it another way, how would you defend yourself in court if you were wrongly accused? What legal defence would you employ? Or would you just accept that there's simply no way to defend yourself and pay up?

Or do you have ways of circumventing the legal system that aren't available to us mere mortals?

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