Category: South West TV; London
Inside Out, BBC ONE London and South West, Monday 12 September, 7.30pm
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 BBC ONE.
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.
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.
With the LTi 20-20 speed gun being widely used, this could lead to motorists receiving unfair fines.
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."
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.
He says: "Very roughly, without doing any calculations, we are talking about the camera moving about the thickness of a human hair."
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.
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.
Wrong speeds of up to 53 mph were displayed by the gun.
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.
The company adapts the American LTi 20-20 guns to follow British specifications.
Presenter Sam Smith says: "Unfortunately Teletraffic, the Police and the Home 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."
The Association of Chief Police Officers claim the experiment was 'misleading' as the UK-approved speed gun uses different 'error-trapping' software.
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.
And NASA then told Inside Out that the version they use is the American version.
All of which seems to suggest that the UK and American speed guns are identical.
Using the Freedom of Information Act, the Inside Out investigation has also discovered that the Home Office does not test for the 'slip effect' as part of the approval process for these devices.
Notes to Editors
The LTi 20-20 speed gun is used by the Police and Camera Safety Partnerships across the UK.