On Fri, 18 Feb 2005 18:53:51 +0000, Paul Terry wrote:

In message , Chris Tolley
writes

One frequently sees plates that are so filthy that no camera would pick
up any image.

The most common type of device (GATSO) makes an infra-red image as well
as a photographic one.

I didn't know that. Fascinating.

--
Not a good picture, but certainly an informative one:
http://gallery120232.fotopic.net/p10862746.html
(A "surfer" hanging on to the back of a Manchester tram in 2000)