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Speed cameras have been the focus of motorists' anger and frustration for years, although we are told repeatedly that they are an effective means of reducing death and injury on the roads. But is this really the case?
Whether speed cameras actually do save lives seems an easy assertion to test: measure the numbers of casualties at a site over a period, say two years; introduce a speed camera; re-measure the number of casualties over an equal period, and any reduction is due to the camera. But it's not really that simple. Many other factors are at play that might make cameras appear to be more effective than they really are. And these factors are often ignored when evaluating the performance of speed cameras at improving road safety.
Do speed cameras actually save lives?
[...] In road safety data, there is a general tendency for collision incidents at a site to reduce anyway following a short-term rise in their number, without any treatment (such as a speed camera) being applied. In statistics, this is known as regression-to-the-mean (or RTM). We also know that the long-term trend in collisions has generally been downward due to factors such as improved vehicle safety and better driver education[PDF].
So if we observe a reduction in casualties at a site following the installation of a camera, we need to ask how much of this reduction would have happened anyway (the RTM effect)? How much is due to general trends in road safety? And how much can we actually attribute to the camera itself?
[...] To make matters worse, half of the UK's fixed speed cameras may not even be turned on. So the situation is far from simple.
Methods to accurately account for RTM and trend often require knowledge of advanced statistics which may not always be available within a road safety team, and so it is likely that these confounding factors are not being considered consistently across the country.
[...] So, do speed cameras save lives? The answer is almost certainly yes, but probably not always to the extent that people are led to believe.
https://theconversation.com/do-speed-cameras-really-save-lives-87701
(Score: 2) by Dr Spin on Wednesday November 22 2017, @09:31AM
May be not the same here (UK), but speed cameras in areas where the limit is over 30MPH are probably a significant cause of accidents because plonkers see the camera in a 50MPH limit and suddenly brake to 30. The cars behind them are way to close and not expecting it - the further back, the less they expect it, and a wave of slowing propagates backwards, growing steadily, until there is an accident 1/2 mile back from the camera. Of course the Bill say "nothing to do with the camera - that's another 1/2 mile down the road". Any truck driver on the A406 will tell you this happens at least once a week. Of course not all the accidents are fatal.
Meanwhile, in London, we now have the plague of cameras in 300 foot long sections of 20mph limit in major roads. Since most traffic in London does not exceed 7MPH anyway, people rarely bother looking at the speed signs, so this must be a major money maker - and not just for the contractors painting all the additional signage. They are probably good business for undertakers too - people (mostly cyclists) expect everyone to obey the limit, and pull out without looking properly more often than usual in front of the kind of wally that does not obey any limits (motorcyclists, mostly).
Warning: Opening your mouth may invalidate your brain!