Safe Speed Forums

I'm not taking. As you say, there will ALWAYS be some perceived range difference in the reflected light. Sometimes a greater range (= minus 0), sometimes a smaller range (= 0 or plus 0).

If it is possible to intentionally defeat the error trapping software (as shown by Paul Clark) to produce a false reading, it must be possible to do so unintentionally because of random factors (such as hand shake, gust of wind, vibration, to name a few). Consequently, it is impossible to reliably assess how often such errors occur. It could be easily be (say) 1 in 25.

That would not be so much of an issue if the possible error could be shown to be always less than the enforcement tolerance or if the scale of enforcement was such that the incidence of wrongful enforcement would always be numerically insignificant. As it is, we have possible speed measurement errors which can comfortably exceed the enforcement tolerance and a scale of enforcement running to (just for the LTI 20:20) hundreds of thousands per annum. So there is a strong probability that a significant number of the enforcement penalties are wrongly (and wrongfully) imposed.

You have all been discussing having the laser slip over the surface of the target due to panning.

In fact the target is MOVING, so it is entirely possible for the target to slip across the laser, and produce the same effect. In addition, the passage of the vehicle is likely smoother than the movement of the laser kit especially at long range - making the following less likely:

The slide could just as easily be vertically up the steeply sloped front of a vehicle such as the VW Sharan, or the Ford Galaxy!

The internal software is basically monitoring a range finder, with a high sample rate. It would notice a jump from one vehicle to the next only if it detected the jump in range offered by the gap between the vehicles. At long range you could make that jump in a very short space of time if you panned the equipment, just as a timing strobe appears to freeze the movement of the marks on your engine!

Trying to manually keep a target in the cross hairs at range is difficult. It calls for the deflection to anticipated - ie to move the aiming point with the target, and match it's speed. With a small arm, this is aided by including tracer rounds to guage the effectiveness. It would appear that the LTI 20-20 has no record of where it has been aimed - the red dot in the program was added to illustrate the problem - it is not recorded in normal use. Only the assertion of the "fully trained" operator that it was correctly aimed sits between conviction or not. Anyone who has seen film of tracer fire will see even with that aid, it is difficult to keep the target in the sights!!

The program clearly showed that TEN sample readings were correct. The ELEVENTH was clearly not - with two cameras giving different readings.
It is now up to the manufacturers to prove conclusively with relevant data that the US or the UK version is capable of trapping those errors.
Tests should be independently scrutinised to ensure Mr Frank Garrett is not acting as a charlatan!!
There is an often heard comment along the lines of "Would you buy a used car from this man?"Would YOU accept the word of somebody who was selling something which he will not allow you to inspect?
Would YOU accept the endorsement of somebody who said posts "timed out" and were deleted? Who claimed that photographs of a talivan concealed by undergrowth were taken when one was not there?

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

Two possible solutions: (FWIW)

1)These devices should be fitted with an accelerometer which detects the slightest movement and invalidates the reading if there is any.

2)All speed readings should be taken by two separate instruments, and only be admissible if both instruments corroborate exactly (time, speed, distance)

Cheers
Peter

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so

Camera operator, you seem to be a reasonably knowledgeable person, especially in matters relating to this topic. Good.
Two questions.

1. Do you genuinely, personally believe the the allegations made in the BBC programme are groundless and do not apply in any significant way to UK speeding convictions?

2. Why would the SCP's and related civil service entities (publically accountable bodies) not wish to reassure the public by assisting in independant and properly scrutinised testing?

Reasoned answers would be greatly appreciated (i.e. I would consider Yes/No alone for question 1 as insufficient).

Agree totally with that - the point I was making is that it might never read the correct speed, just that since some are "more wrong" than others they are "more obvious".

Do you think an operator would notice the device reading 35mph when the vehicle was really doing 30mph?

Spot on correct! Any SUSTAINED relative movement between laser beam and aiming point will generate this error. For example if an operator does not bother to track a moving vehicle at all.

It has to be sustained (continuing in the same direction) otherwise the averaging of the 40-odd samples will tend to correct any error.

There was an article in the Daily Mail today, pretty much the same content as the Mirror, about 1/4 page worth. Another 4 million pairs of eyes!

edit: Scanned by "Braindead" (!) at PePiPoo:
http://img202.imageshack.us/my.php?image=lti20206lv.jpg

Gareth

Absolutely, but only 'sustained' for 1/3rd second.

If actions like aiming pans take a couple of seconds, the critical error may not appear to be a 'sustained' movement at all in a subjective sense.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Not just the side to the cars but bonnets.

how long is a bonnet? say 3 or 4 feet? but at a distance in a camera it will seem like a narrow strip yet the slip effect could be a significant distance as the car moves towards the camera.

... and at a distance of almost 600 yards, as someone close to me got gunned at, the gun wobble would have to be.. how much? Let's assume the gunner was aiming for the plate but slipped almost half a car width - 3'.

3' in 600 - 1/60th of a radian - 1°. For a gun only just over a foot long - less from lens to pistol grip - that represents a lens movement with respect to the grip of... substantially less than a quarter of an inch - less than an 1/8th of an inch movement of each hand if they go in antiphase. Add to that the possible need to be panning if the car is not going straight towards the policeman.... I'd certainly be wary of confirming capability to achieve this degree of accuracy - and I was once a marksman with a .303".

I believe there is no alternative to substantial refunds and compensation now this doubt has been brought into the public domain.

I expect his doctorate is far more relevant to his work than the chief of a certain southern camera parnership. The partnership repeatedly used the Dr title in all their publications, but after enquiries the nature of their qualifications has never been disclosed.

One would hope that it is related to transport, safety, the sciences or similar but I did some research and I am pretty sure that it is sociology, something about immigration, certainly of no relevance to road safety. The fact that she doesn't want it released is a pretty good indication too, most people would be delighted and proud to talk about their work.

Gareth

"Express" (John Ingham) awarded one whole page to the story - highlighting the need to keep still when using the device. Anyone who takes photos knows hand shake on pressing the shutter in inevitable - thus pros use tripods!

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Just to clarify.

Dr. Clark has a PhD in the field of Lasers and Electronics. His thesis was entitled "The Avalanche Photodiode at High Frequencies". (Incidentally the Avalanche Photodiode is used in the LTI 20.20).

Dr. Clark's first degree is in Electronic and Electrical Engineering. He is a Chartered Engineer, Fellow of the Institution of Electrical Engineers and Fellow of The Institution of Highways and Transportation. He represents the UK as the Expert on the European Standards Committee for Vehicle Detectors and was elected Chairman of that committee.

Dr. Clark has a number of patents in his name.

His detectors are used all over the place on roads all over the place - he was very much involved with the Trafficmaster system for example.

Need I go on?

On my video, there is a 0.18 second gap between the error 3 message and the timeout. Hardly the 0.3 seconds we are assured of.

The cross hairs do not touch my car at all prior to the speed reading appearing and at the distance of 720+ metres the shake was very pronounced. It is the opinion of my expert, that the reading was that of slip on the road surface.

This is easy to see, but it is ignored as the CPS and Scamerati continue to persue me. Yet another court date on its way.

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Sink the scameraships
Give us back our Police Force

Are you suggesting that the scope should be aimed at the numberplate during the process of measuring the speed?
If you are, then you should revisit the video of the motorcycle, as the bike is tracked at long distance throughout the clip, and if you can hold the numberplate as a target at that distance, you should be shooting for Britain at Bisley, or become a sniper in Iraq!!
The bike spends little time in the centre of the frame, let alone the number plate!!

_________________
Time to take responsibility for our actions.. and don't be afraid of speaking out!

I think you're being generous there. Say it's being used at 500m. If we slip up the bonnet, that's maybe a deflection of 1/3rd metre at the target. We can infer the movement at the device by similar tiangles. The big trangle is 1500:1. The small triangle at the gun must also be 1500:1 - the gun is about 200mm long so the 'nose deflection' only needs to be 0.13333mm

I defy anyone to squeeze a trigger without inducing a movement of 0.2mm!

It's dead, but it won't lie down.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Camera Operator,

Can you please confirm that bridges do not move at all when trafficked and even if they did, would have absolutely no effect on the speed reading taken.

Can you also confirm that you have never ever been buffetted by passing vehicles when standing on a bridge and taking speed readings.

Thanks

"discredited by two exclamation marks"

Three spellings of 'triangle' in 9 words. I don't believe it! Own up, who's stealing letters out of my words?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I'd go further Mad Moggie. Not only is it necessary to use a tripod to absolutely remove any shake, it's also important to use a cable release or some other remote device to trip the shutter so you don't even have a hand on the camera at all. And remember that the best SLR bodies all have mirror lock up as well so that even tiny vibrations from "mirror slap" can be elminated before releasing the shutter. (But then you're a Leica lout aren't you? No mirror? )

Anyhow, quite a contrast with a tripod mounted but hand moved, or even entirely handheld dodgyscope being aimed at a moving vehicle 600 plus yards away, and for all we know by an operator stoked on black coffee . How on earth can they possibly expect us to believe the point of aim never wanders enough to cause slip error? AIUI the criticism is not that it will inevitably happen every time, but that it is possible for it to happen any time. It might be only one in a million, but it might also be one in a thousand or one in a hundred or one in ten. Bottom line, it wasn't thought of, it wasn't looked for and it isn't in the interests of the government, the partnerships or certain police forces to admit the possibility now.

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