Why are police ANPR systems so inaccurate?
I was stopped in a brand new car (a few days since delivery) by police saying my number plate had come up as a 'stolen car' on their ANPR equipment. When the police checked the actual registration, which they read off the car, everything was fine. Concerned about what was clearly an ANPR error, I enquired of the police authority what explanation they could offer. I was told the car registration was so new it probably had not yet been entered on the computer; this explanation was of course nonsense, since if it hadn't been entered on the computer it couldn't have been detected by the ANPR.
Under Freedom of Information I requested the criteria on accuracy for police ANPR equipment. Apparently all police forces follow National ACPO ANPR Standards (NAAS), which require 97.5 per cent accuracy. Whilst that sounds good, it means 2.5 per cent error is acceptable which is one vehicle in 40 or, on the busiest sections of the M25, up to 60,000 vehicles a day. Readers should be aware that one time in 40 they could be falsely prosecuted. I would suggest this casts doubt on the use of ANPR where it is the only evidence (e.g. speed restrictions at roadworks).
Under Freedom of Information I requested the criteria on accuracy for police ANPR equipment. Apparently all police forces follow National ACPO ANPR Standards (NAAS), which require 97.5 per cent accuracy. Whilst that sounds good, it means 2.5 per cent error is acceptable which is one vehicle in 40 or, on the busiest sections of the M25, up to 60,000 vehicles a day. Readers should be aware that one time in 40 they could be falsely prosecuted. I would suggest this casts doubt on the use of ANPR where it is the only evidence (e.g. speed restrictions at roadworks).
Asked on 25 May 2012 by KR, Marlow
Answered by
Honest John
Excellent point, well made. This is a campaign issue. It is utterly ridiculous and totally unfair to convict drivers on the basis of this 'evidence', which also relies on enforcement of the laws governing the making of number plates. In fact these laws are simply not enforced, so it is still quite easy to get a fake set of plates made up (copying those from an identical make, model and colour of car) and be relatively immune from prosecution.
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