Safe Speed Forums

It may not necessarily be an exercise in logic, but its certainly based on dodgy logic I'm afraid. The conclusions don't add up because the two data source, whilst apparently connected, are in no way directly comparable, the logic involved in such a suggestion spurious. Any estimate drawn by it is therefore fallaceous.
I repeat, what would we expect to see happen if the percentage of speeding drivers went up? Would the roads become more or less safe?

It is a little 'wild' at present, but that's by no means the same as 'fallaceous'. It's being discussed in Brainstorming, and not being presented as a final argument. However, the logical foundation appears sound when the eventual target of any conclusion is speed enforcement practice. Speed enforcement misses it's target because its main effects are concentrated on free flowwing conditions where excessive speed crashes must be rare.



That's not really a valid question because the answer is massively dependent on the reason for the change in behaviour. If for example the percentage of speeders went up because drivers became more reckless then we could be pretty certain that crashes would increase.

On the other hand if the percentage of speeders went up because of widespread speed limit reductions we'd expect little change in risk.

One final example, if we're mad enough to implement ISA and the percentage of speeding drivers falls towards zero, I'm absolutely certain that we'd see a large increase in crashes.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I agree entirely that crashes would increase markedly, but surely they would have little to do with speed directly, and much more to do with lack of concentration and less personal responsibility.

I cannot see how you can argue that speeding drivers are safer based on the figures you have. It's all about context, and a fast, observant, progressive driver may be safer at 80mph on some NSL roads than Mr Flat Cap at 40mph, but that doesn't mean that a speeder is safer in a 30mph zone.

You could say it's not about quantity, but quality, of speed.

I'm not making that argument (although I accept that it might look like it on a quick read here and there in this thread).




Or the context of the speed, yes.

But the broad generality does lead to a clear conflict with the speed kills claims.

If we use matching assumptions to those that make the speed kills claims (drivers must slow down because speeding is dangerous), then look at normal places where drivers are speeding - we typically find 60% speeding.

If we then look at the proportion of crashes that have 'speeding' as a contibutory factor (3%), this really is entirely at odds with the speed kills proponents' expectations.

Surely if 'speeding' is more dangerous that 'not speeding' we should expect to see more than 60% of crashes involving speeding as a contributory factor?

I fully understand the truth of this - routine speeding by responsible motorists does not cause crashes, and rarely contributes to crashes. Drivers slow down in areas of danger and are generally at far greater risk of crashing in those places where hazards are greater and speeds are slower.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Paul, I think that is the problem with this line of thought. The speed kills claims fail to stand up to any proper scrutiny, and that means that trying to turn them around to your advantage will fail for the same reasons. It's too simplistic. There's no way you can say that speeding is generally safer than non-speeding. The good thing about this discussion though is that it highlights how irrelevant speed limits are to safety, because neither "side" can argue convincingly which side of the limit we should be on.

No no, look... this is 'brainstorming'. I introduced the information as 'faintly ridiculous'. I'm REALLY not making the argument that you think I'm making. I'm exploring a conflict in the data that appears to offer some support for our position.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

OK, OK , going back to your previous post



You already have this pretty convincingly from the camera placement rules which define a speeding "problem" as 20% of drivers above the limit. This means that the competent and careful drivers (85% percentile) are both safe, and breaking the speed limit.

Oh sure, but having some great arguments doesn't mean you can't use another.

I also live in a sound bite world (and I really wish I didn't). I have to be ready with smart and quick counters to all sorts of claims that the 'speed kills' lobby makes. If I can stick another arrow in my bulging quiver I'll be happy. If i can't, well, hey, it was worth a try!

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Instantly, if you're not watching out for them.

I take your point, though - although I might not agree with some of your figures. I make the braking time from 30mph closer to 1.5 seconds - which is equivalent to 0.75 seconds in pre-braking time.

Cheers
Peter

What it appears to indicate is that the "type" of speeding that is generating the vast majority of offences, ie "ordinary" safe motorists doing a few mph over the limit, is completely irrelevant to "speeding-related" accidents.

Unless and until stats are available that actually classify speeds in accidents in more detail than just "inappropriate but legal" and "exceeding posted limit" it will be impossible to analyse how speed really contributes and relates to accidents. You could do with estimates of the speed of the vehicle being included in the stats gathering - I'm sure that accident investigators attempt to derive a figure, so why not use it? A table of "Percentage" v "Speed +/- limit" could make very interesting reading, but, with my Devil's Advocate hat on, I'd suggest that it would not prove what "our betters" would like it to prove!

An example... The was a very serious accident in my region a few months ago where either 4 or 5 young people were killed in one accident involving two cars that were overtaking other traffic. It took place in a 50mph limit, and the major official contributing factor was "speed in excess of the posted limit"... The speed in question being some 95mph. I would venture to suggest that drivers willing to take risks like that are not going to be discouraged by the presence of speed cameras, but these types of accidents are being used to prop up claims that "speed kills" - and thereby aiding the criminalisation of large numbers of perfectly safe drivers.

(End of rather "woolly" part-gathyered thoughts)...

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"Politicians are the same the world over... We build bridges where there aren't any rivers." - Nikita Kruschev

pogo's post has reminded me of something. Anyone know when we are likely to get info from the new STATS19 forms?

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Make everything as simple as possible, but not simpler - Einstein

Yeah. September 2006. They are due to be published in annual report RCGB that comes out about 9 months after the year of the data.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Sept 06? Hells bells. That's national results presumably? Any danger of getting info from individual forces earlier? Just keen to see how often the "speeding" box gets ticked as opposed to the "excessive/inappropriate speed" one. IIRC didn't the early STATS19 like forms used by 2 or 3 forces back up what we're saying about the difference between excessive speed and speeding?

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Make everything as simple as possible, but not simpler - Einstein

Perhaps it would help to illustrate the link if we introduce an intermediate measurement to connect the two events. For the purposes of this argument lets assume we have an accurate means of scoring driver quality on an index of 0-100. Let us further assume that this is a "pure" measurement, ie it doesn't down-score drivers for arbitrary legal errors, only for directly attributable safety errors.

Now what relationships would we expect to see (a) between DQI (Driver Quality Index) and collision involvement, and (b) between DQI and incidences of speeding under free flowing traffic conditions?

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!