I tend to agree with Snazy. Just having a look round the internet, most sites are arguing that cameras haven't actually reduced accidents or deaths - some say they've increased accidents.

So the evidence seems marginal at best. It reminds me of a an argument I once heard about CRB checks - somebody was saying that they cost a fortune and don't actually work that well. You'd save more lives by putting money into other things that claimed more lives. Others said they were a price worth paying.

If 95% of accidents are caused by something other that speeding, then it might be the case that the emphasis is in the wrong place.