What about average speed cameras? We have a lot just over the forth bridge now, i can only see forward facing unless the other carriage way gets you from behind, but you'd think that would mean a really big field of view for an accurate picture?
We also have just had Bus Lane camera's installed by the local council, they never got of to the best of starts, picking up people before there active time, picking up people crossing the bus lane to enter a street. I think these to are also only forward facing.