Category: South West TV; London
Date: 12.09.2005
Printable version
Inside Out, 91Èȱ¬ ONE London and South West, Monday 12 September, 7.30pm
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Claims that a hand-held speed gun - used by Police and Camera Safety Partnerships across the UK - can give an inaccurate reading by 'slipping' are made by Inside Out tonight at 7.30pm on 91Èȱ¬ ONE.
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The 'slipping' effect is caused when the gun's infrared pulses are disrupted by the operator moving the beam down the side of the vehicle instead of keeping it steady.
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When this happens, the gun can be effectively tricked, interpreting the movement of the beam as speed, and the length of the car is added to the distance actually travelled.
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With the LTi 20-20 speed gun being widely used, this could lead to motorists receiving unfair fines.
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In tonight's programme, Dr Michael Clark, independent consultant to the traffic and communications industries, commenting on the effect of a potential 'slipping' error, says: "If someone's doing just below 70 mph on a motorway, that puts him up in the nineties and they're going to be done by the police for sure."
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Professor of engineering and author John Brignell believes that for an operator, pointing the gun at a car 500 metres away, the movement needed to slip off the number plate and down the side of a vehicle is minute.
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He says: "Very roughly, without doing any calculations, we are talking about the camera moving about the thickness of a human hair."
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And even in an experiment carried out by Inside Out presenter Samantha Smith, pointing the gun along the side of a stationary car, the device registered a speed of six mph.
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When the test was then carried out on a truck travelling at about 30 mph, a false result was obtained seven out of 22 times.
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Wrong speeds of up to 53 mph were displayed by the gun.
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Teletraffic, the importers of the UK-approved LTi 20-20 speed camera, claim it is impossible to register a false reading from a moving target.
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The company adapts the American LTi 20-20 guns to follow British specifications.
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Presenter Sam Smith says: "Unfortunately Teletraffic, the Police and the 91Èȱ¬ Office declined to take part in the programme - which meant we were unable to obtain a British version of the LTi 20-20 for our experiments, so Dr Clark simply proved such misreadings can happen with the American speed gun too."
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The Association of Chief Police Officers claim the experiment was 'misleading' as the UK-approved speed gun uses different 'error-trapping' software.
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Yet a report, obtained by Inside Out and written by Frank Garratt, Managing Director of Teletraffic, suggests both versions of the LTi 20-20 are the same because the gun used by British Police is identical to the version used by NASA.
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And NASA then told Inside Out that the version they use is the American version.
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All of which seems to suggest that the UK and American speed guns are identical.
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Using the Freedom of Information Act, the Inside Out investigation has also discovered that the 91Èȱ¬ Office does not test for the 'slip effect' as part of the approval process for these devices.
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Notes to Editors
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The LTi 20-20 speed gun is used by the Police and Camera Safety Partnerships across the UK.
