I have just returned from the United Kingdom, where they use traffic cameras on highways and secondary roads.
I drove more than 1,000 miles during this trip. On the principal highways, the traffic cameras are identified with a sign, usually about a mile prior to the actual unit, that can be clearly seen. On the secondary roads, it's a different story. They are virtually hidden by trees, etc., and you only know that they are there when you see a flash of light.
On the highways, drivers usually slow down when they see the signs from 80 mph or more to around 60 mph or less.
The effect on the traffic is simple: it slows down to a reasonably safe level, but it is short-lived. On the secondary roads, the effect is more positive. Because there is no warning sign, drivers tend to keep within the limit at all times.
As in the U.S., the fine can be substantial, and you will lose points for each offense. The local county is responsible for maintaining the cameras, and they share in the fine collections.
However, a recent review of the system shows that the vast majority of the cameras are not actually taking pictures as the counties are on a tight budget, and this is not seen as a priority.
Geoff WheatleyHilton Head Island