M4 Scamera Results
Discussion
Just had a call from the BBC, apparently the "Safety Camera" Partnership have just published their accident figures for the period since the cameras were placed on the M4, it seems that accidents have reduced by 64%.
Does anyone know where accident figures for previous years can be obtained?
I'd like to check the figures to see if accidents always fall in the summer months (as you'd expect) before I make any comments.
Does anyone know where accident figures for previous years can be obtained?
I'd like to check the figures to see if accidents always fall in the summer months (as you'd expect) before I make any comments.
HMSO publishes stats for accidents, I forget the name of the publication though shouldn't be difficult to find. Only thing is, when I was working in the accident investigation field, we couldn't get reliabel figures within 18 months, such is a the QA/blatant fiddling, (oops did I type that out loud?).
Anyway, accidents would most probably go up in the summer, more traffic leads to more accidents, even though in winter poorer weather can contribute to more accidents. All depends on how you present the data; will make a significant difference whether you present accidents per mile travelled, (roughly constant seasonally), per vehicle, per vehicle per mile etc etc. You also need look at the type of accidents. Single vehicle off road type accidents are more common in the summer, especially on a Friday and Saturday night, due to loss of control when out hooning around.
Year on year comparisons are very unreliable. You get a regression to the mean effect, and with so many data points, (i.e. different sites), you are statisticaly bound to have a reduction in incidents at some of the sites cameras are placed. Yet to see a reliable metaanalysis of this though.
Come to think of it, I've yet to see any reliable evidence to suggest accidents are prevented by these things, and they've yet to be able to convince me that they are a positive contribution to road safety. I'll accpet them in towns by schools etc however..
Anyway, accidents would most probably go up in the summer, more traffic leads to more accidents, even though in winter poorer weather can contribute to more accidents. All depends on how you present the data; will make a significant difference whether you present accidents per mile travelled, (roughly constant seasonally), per vehicle, per vehicle per mile etc etc. You also need look at the type of accidents. Single vehicle off road type accidents are more common in the summer, especially on a Friday and Saturday night, due to loss of control when out hooning around.
Year on year comparisons are very unreliable. You get a regression to the mean effect, and with so many data points, (i.e. different sites), you are statisticaly bound to have a reduction in incidents at some of the sites cameras are placed. Yet to see a reliable metaanalysis of this though.
Come to think of it, I've yet to see any reliable evidence to suggest accidents are prevented by these things, and they've yet to be able to convince me that they are a positive contribution to road safety. I'll accpet them in towns by schools etc however..
No reduction in crashes on the M4,according to this:
www.pistonheads.com/speed/default.asp?storyId=11286
www.pistonheads.com/speed/default.asp?storyId=11286
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