Originally Posted by scottf
I'm not saying they are like that in order to catch people out- the large yellow signs should be warning enough but they don't need to be painted bright yellow like speed cameras do they.
No, they don't need to be high visibility.
The type of cameras used are different to the ones used for speed / red light enforcement. The original type (Hillsborough, Wicker etc) are CCTV cameras, a bit like security cameras, which are observed by operators at a control centre. The new ones are automatic, so are smaller because they don't need pan/tilt mechanisms.