Have you checked how the "accident blackspot" speed camera locations were chosen?
Not because average levels of accidents/fatalities were high, but because the previous years figures were high compared to the average.
IE so that they could "prove" the accidents went down after installation.
Having said that, locally there was a big fanfare about the big reduction.
But for some reason the two periods considered were, as far as I can recall, overlapping, didn't correspond to the camera introduction, weren't for a "sensible" time frame, and, though they were supposedly published in detail on the council website, I STILL haven't found them half a year later, and they STILL haven't told me where they are hidden! : - (