In the UK fixed speed cameras are common.

The problem for me is that they are put at places where people tend to speed, and that is often because it is a major road running through a village. Instead of building the proper infrastructure to allow traffic to pass through we just slow it down.

My second problem with speed enforcement is it has caused a shift in policing. Speeding is an absolute and so is cheap to police and prosecute so gets 100% of the enforcement effort, ignoring tailgating, undertaking, lane hogging, lane indiscipline...etc. All of this can be just as serious, and I feel (as a regular driver of some of the UKs busiest roads) are getting worse. I would much prefer to have a police officer in a car enforcing the rules than any fixed speed camera