I wanted to quote more from you, but I’ve decided to continue with the relevant otherwise the thread will become unreadable.
Jub Jub wrote:
Forgive me for not being totally up on the relevant language. So are you saying that when cameras are installed, other measures are put in place, or at that particular site there are also other factors that you could accredit with a reduction in accidents?
Both.
Other measures are also put in place alongside the speed camera, yet only the speed camera gets the credit for any accident reduction. The A12 had a recent spate of accidents, head on crashes; hence the location qualifies for speed enforcement. At the same time a central reservation has been erected to prevent the head on crashes…..
The other factor is Regression to the Mean:
Jub Jub wrote:
Just because there were 2 KSIs one year, doesn't mean that there will be 2 the next. There are lots of factors involved, which is exactly the point. Sometimes blips happen,
Wayhay! You do understand RTTM.
DfT policy puts 85% of speed camera resource
only at locations where these blips occur.
Jub Jub wrote:
smeggy wrote:
Wrong. People can speed at camera sites and still do, obviously you’ve not been considering my posts properly. And yes it does matter how the accident rate went down; if a method is successful then it should be rolled out, if not then it must be ended such that the resource can be allocated elsewhere which could yield real benefit..
That's an interesting conclusion. Does speeding (above the limit) not reduce at camera sites then? Either people are panic braking or they aren't. You can't claim both sides of the argument.
Actually I can. You actually said (which my response was based upon):
Jub Jub wrote:
it also means that you are no longer able to speed at that point, but never mind
Which is clearly an erroneous deduction because drivers do.
- Some drivers will continue to speed at camera sites, otherwise there would be slightly less than 2 million speeding offences last year.
- Some other drivers will brake; either to some to scrub off excess speed, others to make sure they are well under.
Not difficult to understand it is?
Jub Jub wrote:
No. There are no ways to prove it. There are ways to formulate statistics based on theories, but you end up coming down to odds and percentages.
Invalid comment!
I didn’t come to percentages, that was from the raw data. I used the percentages, without further modification or interpretation, to form the next logical step in the argument. I repeat:
Given that only 5% of the accidents used to justify the placement of a speed camera at a given location have ‘exceeding the speed limit’ as a contributing factor, the camera cannot influence the probability or severity of 95% of accidents. So how can the camera be anything more than 5% effective at reducing accidents? (and that’s not accounting for the unregistered, cloned, joyriders, nutters… as well as the stoned/drunk/distracted drivers who just so happened to be exceeding the speed limit).
Surely you must accept this and realise that this is at adds with the claims of speed cameras being so successful (which we know is subject to RTTM - which you now understand)