I think the Iowa DOT calling BS on most of the speed cameras in Iowa is pretty compelling evidence that they aren't there MOSTLY for safety otherwise it seems odd that our DOT isn't interested in safety. 11+ MPH over the posted isn't especially dangerous in many places where cameras are placed. I don't have a link for that though. That's my opinion.
Yep. One of the things I believe they looked at was if there are other alternatives to increase safety.
One of the cameras rejected, at 14th and Grand in Des Moines, was probably rejected because Des Moines has other options. For example, it could convert that to 2-way as much of it already has been, or reduce lanes to calm traffic through there (and has had a study ongoing on those possibilities).