I am pretty sure the police have to pull you over, i've driven past them doing 3,4,5 over the limit and never got a ticket. I think they wait for someone doing more than just a few K's, then on come the lights and you'll get a ticket.
Cos they could pull you over for doing 64 in a 60 zone, thats gonna take 10-15 mins to pull you over, give you the ticket, tease you with a possible cannary, in the meantime, someone flys past at 75....or 100.
Also the police are more tolerent. The council, ie Fixed camera's, plain cars with a flash in front of them, allow only 5% whereas the police alow 10%. they are a bit more tolerent.
PS, not sure if those figures are accurate.