The thing is that if people find out about where the cameras are they'll slow down and if the people are beating them at their own job, new ideas will be popping up. Not too long later those ideas will be tackled with and a formula to beat it then (wouldn't you know it!) a new idea will come up.
pull up beside bin with a passenger in the front seat.
have passenger grab wheelie bin handles.
drive away accelerating slowly so the passenger doesnt loose the bin.
get to 60/80/whatever then then instruct passenger to 'throw' the handle of the bin away from the car (preferably aiming towards a brick fence or something) and bobs your uncle - one F*CKED speed camera bin :)
TIP: do it in a shitbox car so you dont chance scratching your lovely paint