@Frenchy (or De'il's advocate) Speed cameras are placed at accident hotspots, and their most important job is to get people to slow down through these areas.
Speed cameras are intended to deter speeding by helping to detect and educate those who are not deterred. This helps reduce accidents caused, at least partly, by motorists speeding. But these accidents are not necessarily clustered at hotspots: they are caused where drivers/riders go too fast for a tight bend, or too fast to keep control on a straighter road, or too fast near a junction where others are trying to join/cross the road, or too fast to stop if there is someone or something else on the road, or try to overtake where/when it isn't safe, so that they can go too fast. Which is why route treatments (not just individual sites) and average speed cameras have been successful, even where the crash rate was low beforehand.
And going too fast is also a problem even at places where there haven't been accidents, since going too fast causes more pollution and discourages safer modes of transport(both of which contribute to more deaths than crashes cause directly).
I think the Police, Government and Councils should be using more speed cameras, at least until vehicles are equipped to stop their drivers disobeying speed limits.