not true i am sorry to say.
to obscure your number plate is against the law, if a number plate is not visible in in the positive, they just look at the negative and hey presto it appears, i have seen it done on tv, they also showed cling film on a number plate, same effect
there are two ways round it, one has to do with the way your number plate is fixed,(but you can get prossecuted for obscuring your number plate) the other is don't speed
using hair spray / cling film, also means you get fined for obsuring your number plate
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I also disagree with the other website that says the Truvelo camera uses infra red, the filter is red (infrared filters are dark red, almost black) this is so that you are (as the driver who has just been flashed) not blinded by the white light of a xenon falsh tube, if they didn't have the filter you may claim to have been "temporary blinded" and hit the car in front / pedestrian