ProLaser III speedmeter device legality and reliability of its operation on motorcycles
Published 28 November 2014
© Crown copyright 2014
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FOI release 33172
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The Prolaser III is Home Office type approved to prosecute speeding offences.
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The device was tested on and is approved to measure the speed of motorcycles.
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Laser pulses can be returned from almost any surface. The strongest returns, however, will be from materials that are retro-reflective or nearly retro-reflective. If any part of the laser strikes the number plate, headlights or other reflective areas, any return pulse is likely to have come from these areas. If the laser does not strike strongly retro-reflective materials it is still possible that a speed measurement can be made.
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If the laser does not receive sufficiently strong returns the measurement will be abandoned and it will display an error message. If a speed measurement is reported by the laser, the laser must have received signals strong and consistent enough to unambiguously measure a speed.
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Alignment of the laser sight relative to the target is not expected to drift. Nevertheless, to provide assurance for themselves and the public, officers will usually check alignment before and after each session. So unless a subsequent alignment check reveals an error, the vehicle targeted by an officer will be the vehicle targeted by the laser. Officers are also trained about the size of the laser beam at the target and will avoid targeting multiple vehicles. If multiple vehicles are targeted, however, error trapping mechanisms are very likely to abort the measurement. Even in the unlikely event that a reading is reported from multiple vehicles, the officer will ascribe the reading to the fastest vehicle. This may well underestimate the speed of that vehicle.