DfT denies deliberately misleading on speed cam stats

Indeed

Traffic light cameras get a big thumbs up from me. I'd also like to see yellow-box cameras.

Both connect to frickin' lasers! >;-(

Deviant behaviour

It will also monitor for children in the car, and then check whether you are licensed to be in the presence of children.

It's almost here

If you have a fairly new license plate, it will have an RFID chip. EVSC/ISA is mooted and Galileo is up there to do the tracking. You pretty much get this with charge-as-you-drive anyway (which is almost certainly on the way - making drivers pay at least 4 times for the roads).

You already have two of those

Eye-ball mark one. Simply slow down and the the prat go past (assuming it's safe to slow down of course).

How so?

Given that, from year to year, you can get that much of a change in accident rates through mere chance, it's not a very reliable metric. There is no real comparison, except to say that accident rates at the place where the camera was placed dropped by an amount that is actually within the bounds of statistical error. You can have a 100% change in accident rates on a particular stretch of road from year to year without changing anything, so any claim made for a camera would have to be very, very thoroughly researched and evidenced. So far that hasn't been the case, and what evidence has been presented is usually found lacking on closer examination. As in, they claim one figure and then later claim another.

What about all the places where cameras haven't been placed?

What about accidents that happen just out of the range of the camera?

And what about all the accidents that happen within the bounds of the speed limit? Despite the propaganda the problem isn't speed, it's lack of awareness and distraction caused by too much street furniture - including speed cameras. Bad driving, in other words, to which speed merely adds a little more energy. The number of accidents I've seen happen just before passing a camera are too many to list (and, yes, anecdotal - but they were all caused by people who were, up to that point, driving safely though a little over the proscribed speed, suddenly hitting the brakes in order to avoid getting flashed by the camera with the inevitable result of a rear-end collision).

Speed can increase the damage caused by an accident but speed, by itself, doesn't kill. You can be killed by someone driving at 20 if they hit you right.

What about low-speed daft manoeuvres?

How will a speed camera (or even a fancy-schmancy Swiss super camera) detect a 'daft manoeuvre' made by a parent? In my experience any road, anywhere near a school at the start or end of the day is a complete standstill, so speed cameras would be even more useless than normal.

And I disagree about red light cameras as well - with red light cameras, if there's an ambulance at the back of a queue of cars stopped at a red light, nobody can do anything - if they dare to cross the line, they'll instantly get a ticket, and have no way of arguing the case.

I've never come close to a near miss at a set of traffic lights - not to say that it's not a problem, but, as we all know, green doesn't mean go, it means 'go if the way is clear'.

Wrong!

You're making the assumption that speed cameras are only effective where the limit is 30mph or less. This is complete crap. Do minimal research and you will find that many speed cameras in built up areas are not effective. You seem to be suffering from the tabloid disease of "please think of the children"-itis.

Speed cameras are at their most effective where it would be impractical other road safety measures. Where the limit is higher such things as chicanes and speed bumps are not practical. There are plenty of spots where speeds of say, 60mph are safe but much more becomes dangerous. This is particularly the case on roads where forward visibility is compromised. Consider a priority junction after a blind curve or crest where emerging traffic would have time to see a vehicle coming into view at 60mph, but a car coming into view at 80mph would not only leave the emerging driver no time to react but would leave itself with no time to brake. The recent story on satnavs shows that drivers will ignore a road closed sign so warning signs on a hidden junction will have no effect. In this case road realingment to "unhide" the junction may not be financial practical, indeed the people who complain about speed cameras would no doubt be among the first to complain if an LA spent a couple of million quid realigning a road in such a situation.

If speed cameras do make money (open to debate) it would make most sense if the revenue from every speed camera were banked and saved until there was enough money in the kitty to pay for improvements that would make the camera obsolete. The way I see it cameras are only a stopgap solution.

There is something very, very wrong with a camera that is still pulling in lots of money years after it was installed.

Really?

Or more to the point no. The flash is far too fast and low in intensity to dazzle anybody. And that's assuming unfiltered flash which is becoming less common.

Straw man argument

The automatic corrollary to saying that the figure published is not the right figure is not that the "right" figure is the pubished figure less the number just owned up to.

The actual state of play is that the DfT had evidence that said: at speed cam sites, the reduction in KSI after putting a speed cam in place is x%. The amount of reduction definitely NOT attributable to the speed cam is y%. Therefore the amount of reduction that MAY be attributable to the speed cam is (x-y)%.

Not IS, but MAY. However, i am also aware of work that challenges any claim that the true reduction in KSI is (x-y)%. So it is fair to say that the oft-quoted figure is wrong: not fair to say that we now know that the real figure is whatever is left.

As someone with a healthy respect for stats, this bothers me, because it feels very much like the DfT has cut the ground from under its feet. If they had come clean in the first place, then people would be far more likely now to buy into the reduced figure. As it is, they are in the position of saying: sure, we knew our figures were misleading, but we published them anyway...

Likelihood of people having great confidence in what is out there now? Not great would be my guess.

The irony is that places like Oxfordshire DO appear to have done some of the regression to the mean studies needed...whereas some other partnerships (Devon and Cornwall spring to mind) haven't. Yet, on the basis of what is quoted by officials, it is next to impossible now to separate out junk stats from decent peer-reviewed and critiqued invetigations.

That is a breeding ground for junk stats from all sides, making a total nonsense of the debate. But it could have been all different: if the DfT in the first place had taken note of the various critiques made of their work, done a longer-term study using independent academics considering each of the methodological criticisms made - and maybe also published a gold standard methodology for assessing the utility of speed cams...well, not everyone would have bought into that, but a lot more would.

So if you ask me what the real story is here? A well-intentioned government department getting its comeuppance for being too superior, too economic with the truth - even if that was done at some point for the best possible motives.

jane