I think
SPECS cameras are possibly the hardest to see (no stripes etc) and also the most difficult to trick, since they work on average speed - however, they're definitely visible during the day. I've also heard of a possible way of tricking them: just drive through them on different lanes
:D
edit: the most irritating cameras as far as I'm concerned are the ones on the M25. Annoying sh!tboxes which slow down traffic on an already busy motorway, doing nothing but generating free money. Grr.
EDITED: 15 Jul 2009 08:49 by NUKKLEAR