On 2007-06-09 11:52:49 +0100, Roland Perry said:

In message , at 10:08:05 on Sat, 9 Jun 2007, Andy
Hall remarked:
- The piece of paper is too small to be read on a moving vehicle either
by eye or by camera

They are colour coded sufficiently that grossly out of date discs can
be easily spotted from a distance.

.... and this happens how frequently?