BBC News : Congestion charges face legal challenge

[Roland Perry]

In message <1026843373.2158.10.camel@yeltsin.mthink>, Pete Chown 
<1@234.cx> writes
>Presumably you could attach a fake number plate to your car, so getting
>someone fined for something he didn't do.

Ah yes, like the way only the stupid criminals forget to fit false 
numberplates to their cars.

>You would only need to put
>the plate on for the time it took to drive past the camera, so the
>chances of getting caught would be small.
>
>Of course people might also falsely claim that this has been done to
>them.
>
>To counteract this, presumably the actual photographs will have to be
>retained, not just the number from the licence plate.  This will be a
>more significant invasion of privacy.

In practice, if there's a false positive [1] there's no real need to 
retain the detailed data. Just for the negatives [2], false or 
otherwise.

[1] The faked numberplate is for a car that's paid. As the passes last 
all day (or all week or year etc), if the system thinks you've paid, it 
can let you in and out of London as many times as you want, and it's 
none of their business when you do it - all they need to know is it's 
paid for. The real car owner doesn't care if a fake's doing this too - 
it doesn't cost him any more.  A system to spot the same car in two 
impossible places at once is probably too sophisticated for now!

[2] Cars where there's a fee/fine to pay in arrears, and evidence 
required to justify that.
-- 
Roland Perry