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LifestyleMotoring

Inaccurate Hong Kong police speed guns still being used

Laser guns’ margin of error is too great and allowance for this too narrow, but police will continue to prosecute motorists, while lawyers say there is no appeal for drivers after paying the fixed penalty

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inspector Lam Yam-man tests a laser gun in 2008.
Simon Parry

Tens of thousands of motorists in Hong Kong are penalised each year for speeding, and among the equipment used by police to prosecute them are laser guns whose accuracy was found more than 2½ years ago to be unreliable.

An expert who tested the laser speed guns told police in 2014 that their allowance was too narrow and needed to be increased in fairness to motorists, the Post has learned. Police have continued to use them, however, without making the findings public or increasing the margin of error – known as the “technical allowance” (TA). Instead, police have undertaken a lengthy internal review of all such equipment, and are expected to shortly increase the TA, according to the expert.

Although motorists are still being fined and losing licence points based on the disputed TA, a source familiar with police policy says an interim approach has been adopted. Police will apply a more generous TA and drop or amend prosecutions if motorists in borderline cases challenge their penalties, the source says.

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The controversy dates back to 2013, when local traffic police implemented a TA of 3km/h for its laser guns – meaning a motorist must be registered at 4km/h or more above the speed limit to be prosecuted. Previously the TA had been 5km/h.

Professor of Physics at Hong Kong University of Science and Technology, Tam Wing-yim, explains the accuracy and reliability of laser guns.
Professor of Physics at Hong Kong University of Science and Technology, Tam Wing-yim, explains the accuracy and reliability of laser guns.
In April 2014, Professor Tam Wing-yim of University of Science and Technology tested US-made UltraLyte and other laser guns as part of a process to ensure equipment used to prosecute speeding motorists is accurate and fit for purpose. His tests found that the margin of error for the speed guns was up to 7km/h – more than double the existing 3km/h TA and significantly more than the manufacturer’s claimed accuracy of within 2km/h.
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Some minibuses have speed limiters to stop them exceeding the police’s technical allowance.
Some minibuses have speed limiters to stop them exceeding the police’s technical allowance.
Because only a handful of cases in the tests showed the higher levels of discrepancy above 5km/h, however, Tam recommended to police that the TA be increased to 5km/h.
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