Speeding in terms of breaking the speed limit is a contributory factor in just 5% of all road traffic accidents, but where it is the accident tends to be more severe and more often leads to death and serious injury. Round about 17% of all road fatalities are due to at least some extent to breaking the speed limit.
Thus, on the surface, it makes total sense to install speed cameras at all accident blackspots. This should not be the only measure, but should be one of them. Or should it?
In fact there is very little evidence that installing speed cameras does anything to reduce accidents. On the contrary, there have been many accidents caused by speed cameras. Often these are caused by drivers suddenly noticing a speed camera and applying their brakes sharply, resulting in a collision by a following car hitting them in the rear. This sometimes happens when the driver had not been driving above the speed limit in the first place but has done a knee jerk reaction.
Also speed cameras can simply be a distraction. In areas designated as speed traffic zones many motorists pay too much attention to looking out for them rather than just reducing their speed. When speed cameras are located on major roads the majority of speeding drivers just slow down briefly for the camera and accelerate immediately after passing it.
There is an argument for reducing the speed limit at certain accident blackspots and this is likely to save more lives than simply installing a camera. Injuries cased to a pedestrian impacted by a car travelling at 20 mph are considerably less severe than those that occur at 30 mph.
One of the biggest causes of RTAs resulting in injuries and death is travelling at speeds faster than is appropriate for the road conditions. It would thus seem sensible to impose variable speed limits which depend on road conditions at the time.