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   Inside Out - South West: Monday February 28, 2005


Mobile speed camera
Mobile speed guns are gaining in popularity with the police

Mobile speed cameras are increasingly being used by the police to enforce speed limits, but how accurate are they?

We look at these cameras and see if their claims of accuracy are themselves accurate.

A recent report by the RAC shows that nearly two-thirds of all drivers admit breaking the speed limit on a 30mph roads.

It's not surprising then that the amount of speeding tickets we are all getting are on the increase.

But we discover that some of the equipment used by the police may not be as reliable as they like to think.

In the last year the numbers of mobile speed cameras hidden on motorcycle, police van and cars have risen by more than a third.

That means there are just under 3,500 mobile speed units in the country.

In 2003-4 speeding fines generated £112 million. Of that, £92 million was ploughed back into installing and operating the cameras.

A lot of this revenue is now created by the mobile cameras. It is predicted that by the end of the year they will be as many mobile speed cameras that they are fixed roadside cameras.

But are those mobile cameras as reliable as the police would like to think?

Case One: Paul Cox

Paul Cox
Paul appealed against his speeding conviction and won

Paul Cox was driving towards Plymouth on the A303 Dual carriageway when he was stopped for speeding.

The car he was driving was fitted with cruise control, which he had set to just below 70mph - the speed limit on that stretch of road.

He passed by a marked police car that was carrying out speed checks and was asked to pull over.

The police told Paul that they had clocked his speed as being in excess of 90mph.

He was confident that he had not broken the speed limit and contested the case in court.

Former policeman Paul Cox appealed against his conviction – and won. The court found there were discrepancies in the speed gun evidence used against him.

Paul had the confidence to contest his case, but many simply accept the fines even though they feel they are in the right.

Home Office approved

All the speed guns used by the police and the camera safety partnership must first be approved by the home office. Several type of laser devices used in the UK but they all work on the same principle.

The devices work by sending out a beam of infra red light. Ideally this should be targeted at the number plate of a car, because number plates have a special reflective coating which bounces the beam straight back to the machine.

As the car moves the devices quickly take a series of distance readings, and from those works out the speed of the vehicle.

However the accuracy of these devices has been disputed.

To see how accurate they are we have invited Dr Michael Clark, a leading expert in laser and traffic control, to test some of the government approved mobile speed guns.

Erroneous distances

Diagram showing the reflection effect
A wing mirror and a road sign doubled the distance recorded

The machine relies on the laser beam being reflected back at the gun.

However Dr Clark demonstrated what happens when that beam of light is deflected off another object before returning to the speed gun.

He set up a situation where the laser beam was hitting the wing mirror of a stationary car. He explains;

"What's actually happening is the device is sending out a laser beam that is hitting the wing mirror on the car, then it is being reflected onto the [roadside] sign … it's then coming back off the sign, back onto the wing mirror again and back into the receiver."

As the devices use a distance measurements to work out the speed of a car, Dr Clark believes that such reflections could cause erroneous speeds readings.

The slip effect

diagram showing the slip effect
If the laser doesn't focus on the same area you can get the slip

As the gun calculates speed by measuring the changing distance to a car, if the beam of the gun is moved along the car while taking a reading, this could affect the results.

As Dr Clark explains; "This instrument doesn't know if it [the speed gun] is moving. So it started measuring a little bit further away down the vehicle, now it's a bit closer so it thinks there's a speed reading".

He then pans the speed camera down the side of a stationary car and clocks it doing 4mph.

"This is of course very relevant. If a policeman is pointing at a vehicle going by and he moves it across [the vehicle] then he will get an increased, or indeed a decreased, speed reading."

Dr Clark says that all laser speed guns suffers from the same problem so we thought we would give it a go on a wall with one of the latest guns used by the police: an LTI 20.20.

speed camera showing a reading of 58mph
We clocked a stationary wall at 58mph - now that's motoring

By aiming at the wall and pulling the trigger whilst panning with the device we managed to get a reading of 58mph from the stationary wall - enough to get three points and a fine in urban areas.

Dr Clark has only been demonstrating the speed guns on stationary cars to us, but he says the problems could be worse in real-life situations;

"Because the car itself is moving they have to hold it very very closely on the same point on the vehicle otherwise they will get an erroneous speed reading."

In theory, this means that when doing a speed check, if the operator lets the measuring laser move across the side of a car during the speed check, then the length of the car could be added to the distance the machine uses to calculate the car's speed.

Laser guns typically take their series of measurements in about a third of a second. If a slip effect adds an extra couple of metres onto the distance you travel in a third of a second it can increase the speed registered by anything from an extra one to 30 mph.

The manufacturer's response

Frank Garratt
Frank Garratt says that his devices are accurate

But Tele-Traffic, the UK manufacturer of the LTI 20.20 reject the possibility of getting erroneous speed reading from a moving vehicle.

Frank Garratt, Managing Director of Tele-Traffic, says that his guns are fitted with a technology which will detect any slip effect from a moving vehicle.

If it detects any slippage it will display an error message instead of a speed.

Mr Garratt says the device "traps out any panning error."

He insists that on moving objects errors of more than 2mph are highly unlikely. He says the system could display speeds out by "no more than 1mph, if at all, but in any event 2mph is well within the target parameters".

Case Two: Michael Hall

So far Dr Clark has been involved has an expert witness in 5 court procedures, one of them being his own.

In 4 occasions the prosecution dropped the case. Michael Hall who got clocked by an LTI 20.20 in Southampton was one of them.

Michael Hall
Michael Hall escaped losing his license when speed camera evidence was withdrawn

Michael recalls the events; "I am just convinced that I was at the most 30 [mph] because I checked my speed.

"When I got the summons the police said I was doing 41[mph]".

With Dr Clark's help, Michael managed to have the evidence in his case dismissed.

Michael has his own view on why this happened;

"I think they did that because the video evidence proves that their machine wasn't working properly.

Looking at some bits of the video there were clear errors in what the machine thought what distances were, and if it can't work out a distance it can't work out a speed".

Video evidence

Inside Out got hold of one of the very few police speed check videos which has been released.

We showed the recording from the South Wales police to Dr Clark.

He pointed out instances where the camera recorded speeds indicating the vehicle was travelling in the opposite direction to the way it can be seen going on screen. Dr Clark explains;

"If there is a minus sign in front of the reading that means the target has been measured as going away.

"In this case it wasn't. And that is typical of the errors you will get.

"Here we have negative speeds for vehicles coming towards us - It's a nonsense".

Tele-Traffic commented on the video: They say that even though the video does not represent the event accurately; the laser gun itself was always working properly.

Mr Garratt, the Managing Director, says;

"In that particular case there's no doubt in my mind that, in overall terms the officer did not set up the video element as well as he might have done, and certainly made some operational procedural errors in the way he did that".

Growing concerns

Following a successful court challenge in Scotland in February 2005, the Home Office is now considering reviewing the approval of another type of laser gun.

But as far as the police is concerned, it is the home office who decide what equipment they should use. Superintendent Lawrie Lewis from the Avon and Somerset Constabulary says;

Superintendent Lawrie Lewis, Avon and Somerset Constabulary
"If they [The Home Office] have confidence in them, I have confidence."
Superintendent Lawrie Lewis, Avon and Somerset Constabulary

"The Police Scientific Development Branch and the Home Office have type-approved this equipment.

"They've gone through extensive testing - If they have confidence in them, I have confidence.

"If the Home Office decides for whatever reason that the confidence is no longer there then they will withdraw the equipment".

The RAC say it's important the police get it right when clocking drivers. Paul Hodgson from the RAC says;

"I think it's important for the police, as well as motorists, to know that the cameras are working.

"They need the trust of the motorists, so if a motorist's caught - they need to think they've been caught fairly and squarely.

"If the technology's not working .. then those findings need to be fed into the home office review".

Dr Clark says, "I think that these instruments, or instruments of this type should be reviewed, both in their use, and in the capability of the technology to perform the task that is being asked to do.

"We talk of I think it's in excess of 2 million prosecutions using electronic devices - if only 1% of those prosecutions are incorrect that's 20,000 incorrect prosecutions, and that cannot be right".

See also ...

On the rest of Inside Out
Pushing the limit
Speed - Trading Places
Speed Cameras
Speed Kills
Car Cloning

BBC - Motoring - Safe Driving

On the rest of the web
Department for Transport
Tele-Traffic UK
Lasertech inc
LTI 20.20
LTI 20.20 (Devon & Cornwall Police)
Devon & Cornwall Safety Camera Partnership
Think! Slow Down campaign

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Readers' Comments

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John Evans
ANON states "Fact: hitting a pedestrian whislt travelling at 20 mph will result in a 90% survival rate. At 30 mph this decreases to 50% At 40 mph this decreases to 10%". Well not according to the latest government advertising campaign. They now state that at 40mph 80% of pedestrians hit by a car die but at 30mph 80% live. The harsh reality (from my experience of attending in excess of 100 RTAs involving death and serious injury) is that a pedestrian hit by a vehicle will be, at best, seriously injured and may be killed at speeds as low as 5mph. My experience also shows the impact of the collision varies dramatically according to type of vehicle and accessories fitted to it. The harsh reality is that the majority of pedestrian injuries and fatalities can only be prevented by radical moves to separate pedestrians from traffic - speed limits are not enough. I'm the Hampshire Co-ordinator for the Association of British Drivers and based in Southampton.

On November 15th 2004, I witnessed the most dangerous and prolonged display of dangerous driving I have ever seen, interspersed with a bout of road rage aimed at another motorist; none of which occurred at above the posted speed limit. Although I was able to record the registration numbers of both cars involved, and reported the matter to the police, no action was taken. I made an official complaint, and was informed that due to a limit on the time in which police have to act in such matters (14 days), the law prevented them from doing anything and so a dangerous driver has escaped punishment. In the meantime, I read that a local tennis player had been prosecuted for driving his car through a puddle and splashing four pedestrians - undoubtedly uncomfortable for the pedestrians concerned, but not life-threatening as was the incident I witnessed! My experience suggests that in at least one police force area, dangerous drivers can travel the county's roads with impunity; their actions putting other road users at risk of death or injury, because unless they drive past one of that force area's fixed or mobile cameras at above the posted speed limit, they will attract neither the interest nor the attention of the authorities. What is truly needed is the return of visible, dedicated traffic police units, and for the local force to actually respond to public reports of dangerous driving. A little less "Kodak" and a little more "Kojak" will have a far more beneficial effect in reducing accidents, and might regain the public's faith in the policing of road safety policy.

Marty Hopkirk
The argument is not about speeding and "getting away with it", its about the evidence presented being accurate. Working and driving in a heavily Gatso infested area I am always observing my speed - with the end effect that I drive at 28 - 30 MPH but almost constantly checking my speedometer. I am forced in to this dangerous practice of spending so much time "distracted" from the road because the Gatso's in Blackpool WILL triger at 31 MPH. Even though I can (and have) contest a fine at 31 MPH its time and money consuming.

I have been accused of speeding when I know I was not. The LTI20.20 has been used and I have been back to the site to take photos, trying to get some evidence against this untrue accusation. I took some photos of the mobile camera van and was accosted by the driver who after a brief conversation was allowed to see the equipment in use. He zapped a car in the same place as I was but the distance shown was 561 metres. My photo shows 728.8 meteres. Now his van was in a different place, and I measured it at 70 metres. This still shows a difference of nearly 100 metres? Accurate? I don't think so! Also I have been told that my offence was NOT an 'alleged offence' but is fact! No innocent until found guilty these days it seems.

Rob - the road traffic policeman - completely misses the point. This whole issue is about drivers observing speed limits and still being incorrectly prosecuted, even in these times surely he is not suggesting this is justified? Perhaps if we saw more traffic policemen watching for really dangerous driving (at any speed from 10mph up to 100mph) and pulled the large numbers of people driving with mobile phone under chin (or better still the high numbers who completely ignore speed cameras because they are not taxed or insured) then we would see some reduction in accidents. But time and again we get the same nonsense trotted out by chief constables or humble traffic cops, to justify an exercise that has very little to do with road safety but a heck of a lot to do with revenue generation.

As a Road Policing Officer I am amazed at the lengths the "ordinary" motorist will go to, to blame someone or something else for there own silly mistakes. These people must realise that a combination of factors which include speed,inattention and other factors result in the carnage on our roads every day. The simple facts are that there are more than enough road signs and warnings to alert all drivers of oncoming the speed limits and to say that they simply didnt see these are pathetic. The cases stated on this article are probably a tiny pin drop of cases where the machine "may" have given an erroneous reading, that I find very hard to believe. The point is simple, if you stay within the speed limits you are less likely to kill anyone FACT !!! and you are not ging to be faced with a fine or proceedings, FACT !!

Mike Hall
I have read Mr. Sonumanas comment with interest, and as someone who took part in the program my only comment is to expand on what I said in the interview. I was certain that my speed was legal, and that the police had made a mistake of identification of any offending vehicle. However, after viewing three seconds of the video evidence, I knew that the vehicle was mine and that the measurements looked dodgy. Close examination of the evidence by an impartial expert (not an importer of the machinery) found several anomalies on the recorded evidence. One of these was that two cars clearly metres apart as shown by identifiable street furniture were recorded by the machine as one tenth of a metre apart. An inability to accurately and consistently measure distance means an inability to accurately and consistently measure speed. That is why the police offered no evidence and dropped my case - their own evidence if shown n court would prove that the machine cannot be relied on. Mr Sonumana could well be correct in his allegation of trying to confuse magistrates and judges in many cases, but it does not alter the fact that people just give in and take fines and points in the mistaken belief that the technology must be right. The technology is not reliable enough and at some point (probably when enough magistrates and judges have been wrongly accused) this will be realised.

Charles Bowers
anan, of course, totally misses the point. Whatever the dangers, or otherwise, of exceeding a speed limit, he seeks to convict people of the offence, whether or not they actually committed the offence. As to chellenging the 'verdict' of type approved devices in a magistrates court, it is all but impossible. The credibility given to the device by the mere fact that it is type approved, ensures that the magistrates will always convict. There was one case recently, where a laser device (a Kustom pro-laser iii) was doubted by the court because the car had a governor, which prevented the car going at anything like the alleged speed. Significantly, that case was heard by a sheriff (a trained judge), who does not receive income from the fixed penalties, and therefore does not have a finacial interest in a guilty outcome, as do English magistrates courts.

Paul Furnival
I refer to the comment made by "Anon" (unusual name) and can't help but think you have missed the point of the article. The article is showing that people who are NOT speeding are being incorrectly reported as doing so by the equipment. This means "many of the people who have recieved tickets for speeding offences are decent hard working members of the public" and have been WRONGLY convicted of the offence. This article is not saying its OK to speed, they are saying the cameras should be more accurate. This is simple logic.

Several things could be done that would instantly improve the respect drivers have for speed cameras and the police that use them. First the cameras could be EXCLUSIVLY used in 30mph zones where they might save lives of children and pedestrians in a situation where speed absolutely matters (the difference in deaths with car drivers doing 70mph and 80mph on a motorway is largely insignificant, the difference for pedestrians hit at 30ph and 40mph is). Second the speed fine should be abolished. If this is about SAFETY then removing persistant offenders from the roads by taking their licence is good enough, only if it is about revenue is there are requirement to charge a fine (and incidentally to install cameras on motorways and dual carriageways!).

Chris Walker
All laser devices are supposed to be used from a stationary tripod, with a wind limit defined for the tripod & preferably no direct user contact with the device. Any small movement of the laser device during the very short read time, will induce an error whether it is correctly targetted or not. The police & speed camaera partnerships have taken to mounting their laser equipment in vans & these are inherently unstable, with a large moving weight inside, i.e the operator. If the operator coughs or moves, the WHOLE van moves & thus the laser equipment. I have seen many talivans parked on bridges in medium to strong winds, supposedly recording speeding motorists. More often than not, I'm sure they are recording VAN motion + motorists speeds, often leading to convictions for VAN motion ! I'd suggest that you test that by using a laser in a van aimed at a flat reflective object with a speed reading of zero & then increase the wind on the van in a typical gusty fashion & have the operator move or fidget & see what speeds the target achieves !

I work with similar laser techology, but used in a different manner altogether. However, it still applies that if the laser launcher is turned a tiny amount - the other end is going to move a huge amount - especially if the reflector is a long distance away. It seems there are too many variables in setting up and use for the speed reading to be reliable and accurate. I enjoy driving a lot, and it upsets me that there can be someone waiting round the next corner, or hiding behind a sign waiting to extract money in an unfair way. Personally I would have no problems if there were average speed cameras fitted to 30 and 40 mph zones. The limit is there for a reason (hopefully) and there is no excuse to break them. Doesn't it annoy you when you're stuck behind a poorly trained driver travelling at 40mph in a national speed limit, only to enter a 30mph limit and continue travel at 40mph??!! Why don't we look at driver training instead of having to worry about where the next incorrectly configured/handled laser camera is?

There is a very good saying in industry, “EXPANSION IS THE ENEMY OF QUALITY”. The speed camera business has grown at an exponential rate in the wake of the “Hypothecation” project and as a result, any previous attention to detail has been long been discarded in the pursuit of Government objectives and “performance targets”. It comes as little surprise to hear of these alleged errors and there is another reason why these may have occurred. Previously the accuracy of a laser speed meter would be checked against a Police vehicle with a calibrated speedometer, before and after every shift. However the Government subsequently downgraded these calibration requirements for the sake of convenience. They declared that the internal diagnostic self-check performed when the device is switched on was sufficient to guarantee accuracy of measurement. Anyone with an ounce of knowledge about instrument calibration will tell you that this is complete folly. All scientific instruments should be calibrated against a set of independent, validated standards to assure the integrity of any data subsequently generated, especially if it is to be used in evidence in a Court of Law. This was proven in the Canadian Courts in the case of Regina vs. Tracy Bourne. The judge upheld a defendant’s claim that the evidence from a laser speed gun was inadmissible due to the fact that the accuracy of the speed reading was wholly dependant on the system’s self check and it had not been verified against another calibrated device. I believe this case set a precedent in Ontario and a similar ruling is desperately needed in the UK.

Fact: hitting a pedestrian whislt travelling at 20 mph will result in a 90% survival rate. At 30 mph this decreases to 50% At 40 mph this decreases to 10% notice a theme developing? The quicker you are travelling, the more damage will be incured to yourself, your vehicle, and any other unfortunate object in your way. This is simple logic. I'm sure many of the people who have recieved tickets for speeding offences are decent hard working members of the public, but thats hardly an excuse for excessive speed. Can you all be sure you know what your speed is at all times? And can you all say that you regularly check your speedometer, even if your journey is entirely within a 30 or 40mph limit? How many times have you left a 60 or 70 mph limit, and entered the new speed limit still travelling at excess speed doing that speed. Is everybody aware of what the speed limits are? The example above of Andrew West shows that they are not. 'Sticking to under 70mph' is hardly law abiding when the speed limit for a transit van on that stretch of road is 60! If you recive a speeding ticket it is because you have been caught by a home office approved device, travelling at a speed above the legal limit. If you are convinced of your innocence you have the chance to visit a court of law and put you case forward for a magistrate to decide. If you are not prepared to do this, then take the points and pay the fine and shoulder the responsbility like any decent hard working member of the public would.

Ed F
We have a saleman (Mr Garret) assuring us his products work and a police force not bothered about accuracy as long as the Home Ofice has said it is ok. Trust in the police and its methods and motives with traffic policing are not good as it is at the moment. Independent testing with published results and a police force that listens to the public it is meant to protect is desparately needed to rectify this.

Nigel V.
Given the pyramid financing scheme in place it’s quite clear that this is about money not safety. I wonder how many lives could have been saved by proper road maintenance, checks on uninsured vehicles (10 times more likely to crash) and the real causes of accidents: inattention, tailgating, failing to look, drink, drugs, and poor eyesight.

Doug Turner
I find aran sonumana's comments interesting. I am not a criminal - I have never had a speeding ticket in my life, and never intend to, but I am deeply disturbed by the use of laser speed guns. I whole hearted support the introduction of speed cameras on the UK's roads. Anything which makes our roads safer is OK with me. That said, any enforcement technology which is used HAS to be utterly reliable and transparent. Gatso's, for instance, use two techniques to implicate the speeder (doppler radar and the graticule in the road). The trouble with the laser based devices are many fold: They rely on the operator setting up the device correctly. The operator has to align the laser with the cross hairs on the video. There is no check that this is done correctly. The videos which are presented in court show the magistrates a vehicle under the cross hairs, and a speed. The implication being that if the cross hairs are on the car, then that is its speed. If it has not been provably correctly aligned, then may well be a bogus impression. Has the gun been aligned in two planes or just one? The physics used by the device is not reliable to produce speed readings. A level physics tells you that much. As a result of this the manufacturers have had to build in a raft of filtering logic in an attempt to spot these cases. This hopeless. You cannot possibly distinguish all the cases (is the object moving, or the gun? Is there slip occurring? The techniques outlined by mr sonumana are fine for small errors, but not gross ones. Heuristics, interpolation, error mangification and statistical interpretation are no substitute for real accurate readings. This device is convicting people based on 'logical guess work'. How much diveregence is there in the 'beam' of the device? At 300m how many vehicles are really being targetted, and which one gave the strongest return signal? I can't say, and neither can the 20.20. Mr sonumana seems to imply that the device can differentiate between a moving object and a return from sweeping the device along a stationary one - a neat trick if you can do it! I'd patent it, and set about rewriting the physics text books if I were you! I am an engineer, I know what can and cannot be done with this sort of technology, and it is fundamentally unsuitable to use for which the 20.20 puts it. Lets keep laser measuring confined to those toys that estate agents use to quickly measure rooms, and out of the courts please! We must have reliable devices in the hands of the police. It is grossly irresponsible to prosecute based on the evidence of these devices. I am very worried that whole thing is going to go into 'meltdown', when enough people challenge the 'evidence'; this will result in choas, and millions in compensation. No-one wants that - we just want the speeders off our roads!

As someone who was recently “clocked” by an LTI 20:20 I have been looking at the accuracy of these devices closely over the past few months. My most interesting find about these (and for that matter the amazing Mr Garrett’s Company) is the calibration sheet provided as “proof “that the devices are working properly. In the UK we have a UKAS, The United Kingdom Accreditation Service who are the sole accreditation body recognised by government to assess, against internationally recognised standards, organisations that provide certification, testing, inspection and calibration services. See . Our Local council (Lancashire CC) trading standards use them to ensure that equipment is calibrated correctly, our local road safety partnership (Lancashire CC and Lancashire Police) do not! Evidently it is more important that I am not short measured on my quarter of Werthers Originals, than evidence against me be accurate. Like most thing this seems to come down to money – why bother to accurately calibrate properly when you can simply write out a certificate and have the might of the CPS to protect you from anyone who may choose to question the accuracy of your equipment.

An Engineer
The main problem with these devices is that there is no independent means of checking that they are set up correctly. Remember: the laser beam is invisible and so it is impossible to see where it is actually going. If the targeting mechanism is not correctly aligned with the laser beam, the operator may beleive he is tracking a car when in fact the laser beam is striking something else - such as a wall. Since he is moving the beam along (thinking he is following the car) he would actually be moving it along a wall. The device would then produce a reading from the wall and not the car. Exactly as demonstrated in the program. The speed reading produced would not be the speed of the car. So while Mr. Garratt contends that the device can trap slip on a moving object, it doesn't really matter if the targeting mechanism is not aligned with the laser! I would also be interested to know how the device "knows" an object is moving or not. Surely it has no way of knowing - otherwise it would not let you obtain speed readings from stationary objects The program produced evidence to suggest that devices are being misused in this way. If that is the case then wrongful convictions are inevitable, surely?

Despite massive increase in speeding detection and enforcement the KSI statistics are on the upturn. Any changes are statistically insignificant despite the advent of ABS and airbags etc. It's time to admit that all the cameras do is provide a source of revenue generation for the treasury. We need a return of traffic police to spot poor and dangerous driving practices.

Richard Ceen
Frank Garratt is not a manufacturer; he is merely an importer of the US manufactured LTI20:20. He has no technical qualifications but acts as 'expert witness' for the CPS in many cases where the evidence is challenged. He maintains a claim of equipment infallibility but can never reveal the details of the algorithm that 'traps out errors' presumably because the US manufacturers will not release it. There is certainly some error trapping routine in the 30 distance measurements over 1/3 second that sre used to derive a speed reading. But the equipment has no independednt means of verifying this potential inaccuracy from panning and there are bound to be many occasions when the speed calculated is erroneously high. Fank Garratts partisan claims should be seen for what they are and his financial interests would have disqualified him as an expert witness in an any other legal situation; why not speed enforcement ?

Richard David
This story is utterly appauling. Mechanised justice at its worst! How much do you think it will cost us the poor taxpayer when this speed gun is withdrawn due to its unreliability and the floodgates for compensation for wrongful conviction open up??

Kris Shortland
Tele-Traffic UK are only a importer of the Laser Technologies LTI 20.20, Funnily enough MR Garratt is also the Police forces Expert Wittness. Is there not a conflict of interest here? As proved with private testing at Thruxton Circuit we had a moving vehicle gain 16mph from slip affect. and with the tests we carried out with Dr Clark & Sam we also proved that you can obtain erronoeus readings.

Aran Sonumana
The accuracy of the speed measuring devices has been called into question by what would seem to be dubious challenges, typical of alleged offenders, designed to confuse magistrates and judges not best equipped to make technical decisions. Let me explain. 1. These challenges are typical, why? Look at the web forums that have sprung up that are populated by alleged offenders desperately trying to obfuscate the legal process. 2. The forums mentioned are full of drivers desperate to confuse their tickets issued for speeding with the phenomena Dr Clark has demonstrated featuring within these pages. It would seem 2 offenders have taken this through the court process and caused enough doubt, more likely confusion, to get away with their speeding offence. 3. The laser devices are designed to measure speed of a moving object. It is not surprising that if pointed at a stationary object while being moved either toward or away from that stationary object that the device creates a speed reading. That is exactly right and it is how these devices are supporsed to work. Conversly, how many of these devices are being used to detect moving vehicles while being moved in this manner? NONE, is the correct answer. They are either mounted on a tripod or desk mounted stand or are steadily hand held by a trained operator. They are not moved backward and forward at 58 mph while measuring the speed of a vehicle. 4. The sweep error (produced by either a moving gun or moving target point) is detected by the laser gun in the error trapping mechanism by a method of prediction. The laser device will measure the speed of a vehicle by a time/distance method over a few pulses, once the initial speed is assessed the gun will then predict within a few mm where it expects the vehicle to be on every succeeding pulse. Should the vehicle movement, the profile of the vehicle body or the small movement of the beam cause the vehicle to be measured outwith this small predicted position an error will be indicated and no speed reading will be presented to the operator. Remember all of this is happenning in a fraction of a second so even at high speeds the vehicle will only travel a few 10s of metres at most with its predicted position being known on almost 40 occasions in this time before a speed reading will be recorded. With these few technical facts, the integrity of the Home Ofice Scientific Branch testing and the dubious nature of the objecting defendants I submit that this latest desperate attempt at bringing the validity of laser speed readings of motor vehicles is no more than what it is. Obfuscation of the legal system by those determined to undermine the governments determination to use these devices to lower unacceptable casualty rates on the roads of the UK. The success of such dubious persons would be a tragedy even greater than the deaths and serious injury being suffered by many motorists every day. The BBC seem to have been duped by these individuals without taking the precaution of reserching the web fourums in which they lurk. Please do so and report further on these.

Mark - Tavistock
I'm a responsible high mileage driver with a (thus far) clean licence. I have heard increasing tales of those who have picked up speeding tickets whilst honestly adamant they were within the limit; but felt they could not quibble with technology. All are now paying through the nose for insurance. With a recent proliferation of infra red traps on our roads, the odds of a high-miler unwittingly totting up points and potentially loosing a licence and - hence - job - are really quite worrying. Please, Inside Out Team, push for your research to be taken to a national documentary audience and tested. The reliability of these devices must be established. How many people have lost jobs through unsound prosecution?

Tony Collins, Rugby
The accuracy of speed guns has always been questioned. I remember the BBC TV motoring show before "Top Gear" doing a test at Silverstone. They had a yellow Ford Escort MkI van, (that tells you how long ago it was) which was running on only three cylinders. The van was travelling at walking pace away from the camera. The instrument recorded a speed of 45 MPH. I fear we shall never defeat them.

S Dobson
As a trained and operational user of the Ultralyte 20.20 laser equipment I do not believe that you fairly covered some of these concerns. I feel that you should have demonstrated some speed measurements taken of moving vehicles with a hand held 20.20. Then you, and your viewers, would see that you really do have to keep a steady hand and aim on one point of the vehicle, as any slight movement of the equipment will result in an error message and no speed reading. You should try taking speed readings of traffic with a hand held 20.20 on a windy day! You can get error message after error message !

Peter Burton
You did not mention in your article the effect of non movable objects that may have an effect on the laser gun such as lamp posts, road signs, cones etc. etc. I note that the incorrectly reading laser gun video had a series of road signs that could/would have such an effect on altering a shown speed. Surely conflicting roadside funiture must be taken into account by the Police when laser guns are used?.

If Frank Garratt of Tele-Traffic can say that the equipment can be set up wrong by the operator, How can anyone ever confirm that it is ever set up right. He just does not want to admit his equipment is flawed due to the amount of money he makes from selling it to the authorities.

Paul Hocking
It is a disgrace that otherwise law abiding people are being targeted in such a cynical way by the police and government, for what are petty speeding offences. It makes it far worse that the lasers used are inaccurate, and that their numbers are increasing so rapidly. This sort of persecution by the government will not stop until everyone has twelve points on their licence, and when it further infringes on our liberties and livelihoods. The issue of speed guns in general should be reviewed by your programme, and should be targeted at only those who are doing excessive speeds - ie: +25%.

It is about time the BBC told the truth about speed cameras. They don't save lives, they don't make people drive better - they are just used to gather another stealth tax. Innocent people are being targeted, some lose their licence, their job and in some cases their families. Speeding does not cause accidents - bad judgement and idiocy does. More people are killed in our hospitals through neglect than are killed on our roads - and only 7% of all fatalaties have speed as a contributory factor. It's time to do the decent thing, that many other countries have already done - and that is to scrap ALL speed cameras and bring back the traffic police.

Philip Blair
It comes as hardly any surprise to anyone with a basic understanding of physics that these laser speed measuring devices can be made to lie. All such devices should immediately be removed from service and the so called "Safety" Camera Partnerships, which thrive on increasing road deaths and fines generated by these devices, should be disbanded. The increasing focus on speed enforcement while ignoring other aspects of safe driving has seen the UK experience an increase in road deaths while Germany last year saw a decrease of nearly 12% which they attributed to better car safety and medical techniques. The motorist no longer has any faith in the rule of law on the road as the police are seen to target "easy money" while those actually causing danger go free. Now that the devices used to generate this "easy money" are shown to be flawed it is time for a change in direction before faith in the rule of law and the police is totally destroyed.

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