Safe Speed Forums

Yeah, it might be, but we know what a load of rubbish they're talking don't we?



I can't make the lack of traffic police a big enough factor alone - but I admit that there has to be guesswork in the estimation. The problem is that normal responsible drivers who don't deserve the attentions of the Police seem to be affected too. Check out the bit about "how to have an excessive speed accident" on this page:

http://www.safespeed.org.uk/effects.html

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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

What's the problem, Pres? When an idea is achieving its objective, and doesn't need as much support, it should be run down, or even stopped if it makes sense. No use subsidising a thing that gives no return. Anybody would agree with that. It would be nice if that was the problem, because it would mean we would have licked the speeders! On the other hand, if it needs a bit more nipping down, throw some more at it. I think this is the start, not the end, of the process, though. For instance, there might be large economy of scale advantages in networking and instrumenting the entire M and A road system, for real-time monitoring, routing, control, and data transfer reasons. Imagine, for example, the improvement in emergency service response times with auto-crash detection systems, which self-notify the GPS location to the control centre without intervention. Just one small advantage of the intelligent highways technology that is on the way.

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You would have had a point there if cameras had been used to release the trafplods to do more patrols, but to a large extent they have merely replaced them. The problem I have with replacing trafplods is it's like taking all a builder's tools away and leaving him with one drill. He can still make holes, but no matter how good a drill it is he can't actually build anything anymore.
As for the second part, it's down to cost and value again, mate. I'm happy to pay for coppers to stand around (yes, in the rain too ) with radar guns, providing that it's in a sensible location rather than a honey-trap with an unrealistically low speed limit. It seems to me that there's greater value in pulling idiots at the time of the offence rather than sending a NIP two weeks later. They can also pull someone who is below the limit but too fast for the conditions or following too close, give a ticking off or maybe only a warning gesture to marginal drivers, and having stopped someone can check the car's roadworthiness or the driver's fitness to continue if they feel it's necessary. Their value comes from their ability to tackle more than one type of problem and in a variety of ways. All a speed camera can do is take pictures of someone who's over the limit, and to a large extent those it catches are all treated the same way regardless of how much danger, if any, they posed. At 40 or so grand that it may cost less in the long run, but it's crap value due to its inherent limitations.

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

He also wrote "A computer does not substitute for judgment any more than a pencil substitutes for literacy. But writing without a pencil is no particular advantage". Just because you can do without a particular technology doesn't mean that you should do without it.

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Heh. So after a few years the cameras will just be taken down, the police will concentrate on robbery or strret crime or whatever and speeding will be at an end?

Somehow I don't think so. Unless of course you believe that speed cameras will bring about a culture change in drivers?

This is the 'Athlete's Foot' problem. You get a bad case and slap on the compound. You keep doing that until it goes away. You leave it for a bit and before you know, there it is, back again. Well, speeders are like fungus - you have to keep on treating them harshly until they go away, then they just need a bit of treatment now and again to keep them under control.

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The effects of Athlete's Foot and its mechanism are well established and quantifiable - although, not being a medical man, I cannot describe the exact mechanism, nor quantify it. But the medical profession can, and have done so.
But what effect do 'speeders' have, and by what mechanism? I have not seen a single piece of research which adequately describes the supposed effect by way of any mechanism, nor quantifies it.
Speed limit enforcement can really be described as, in the words of the late Victor Borge, a cure for which there is no disease.

Regards
Peter

Missing traffic pols might not be big enough on its own but is there any evidence for any other factor being a significant cause eg economic growth , increasing safety of cars making people careless? Do we have substantially more illegal drivers than other countries that maintained the trend and without wanting to start a race war, does our increase in immigration match the increased danger levels on the roads? Demographics and the ageing population and perhaps even the lack of free eye tests (how many drivers can't see properly, has it increased?). Cars have got cheaper to own so that has encouraged people on the roads that aren't real motorists just people that just want to get to A to B and don't see car driving as something to be improved upon.

I don't know whether these stats would exist but comparing accident data in terms of vehicle type, make, model, safety features, whether they were used, location, ethnicity, age, gender and social group might show whether there is a change in the kind of people having accidents or whether there are just more of the accident prone groups.

And how would this "now and then" treatment be utilised? You're stuffed if you want to use cameras because you haven't got enough money to run them. Your're stuffed if you want to use trafpol because you don't have enough of them and even if there was the will to hire more it would cost too much and take too long to train for such a short term treatment.

Surely the sensible solution is to bring about a step change in the culture of road safety in the country at large. A system of education, incentive and enforcement for the nutters is eminently more sensible.

You *must* be a member of the scamerati, and I claim my five pounds.

What exactly do you do for a living?

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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

Generally, I’m an engineer. I am a bit of an all rounder, jack-of-all-trades, master of none. Specifically, I have spent the last three decades in the control systems industry on projects related to chemicals production, power stations, nuclear power and oil, spacecraft operations and pharmaceuticals research. I admit I could pick up a bit of work from any spend on ‘intelligent highways’, although I (generally) believe in what I say, even if some of it is pie in the sky right now! Yourself?

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Pretty similar I guess.

1972-1982 electronics design (analogue and digital)
1982-1990 industrial microprocessor consultancy (mostly instrumentation)
1990-1995 advanced computer graphics support
1995-2003 PC consultancy
2003+ road safety campaigner

(self employed since 1982)

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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

Yes, I am slightly familiar with some of that kind of thing. I reckon the engineering experience (economics, politics, disagreement, complexity, trade-offs, feedback, incremental improvement etc.) over a long period leaves a person skeptical about much of the recieved wisdom held by politicians and voters about systems. I am amazed that there is no GCSE in General Engineering that teaches young people about why systems work or fail. After all, from one angle, human advance is all about systematisation.

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Thanks, I'll try and figure out what you mean. In the meantime, to visualise this, we can eliminate cars and roads and the planet and what have you from the problem and represent the problem as Einstein did, i.e. in an inertial reference frame in space. We can imagine two bodies that collide. Let us imagine that the bodies are going along the same line in the same direction, and the leading one is travelling at 17,000 mph, and the trailing one at 17,080. The trailing body will catch up with the leading one (and eventually collide with it) at 80 mph. That is to say, the relative difference in speed at the point of collision is 80 mph. Now, because this is an inertial frame, only the relative difference is relevant.

If we now pretend to be (as Einstein might have said) a casual observer travelling alongside this little dog and pony show on a magic carpet moving along in a parallel line at 17,040 mph, the bodies appear to travel directly towards each other at a speed of 40 mph, with a relative difference in speed of 80 mph.

You can try this for yourself at home. Drive into a stationary car at 80 mph and assess the damage to both cars – it will be similar. Then, in your new car, park up and have a friend drive into you at 80 mph. I can assure than the damage will again be similar in both cases. Then, drive into each other at 40 mph, and again the relative difference in speed will be 80 mph, and again, a similar level of damage will be observed to both vehicles. That is what happened to me in a car – the relative difference in speed was 80 mph and it is largely irrelevant which of the cars was moving. I used to manoeuvre satellite for a living. The spacecraft is doing around 6,000 mph in it’s inertial reference frame, yet the fact that it has a huge kinetic energy is wholly irrelevant, and I could send it halfway round the globe with a small burn. It is only the relative difference in speed that matters.

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You're both right!

One car travelling at 80mph does indeed have double the K.E. of two travelling towards each other at 40mph, but in order to see why this is irrelevant you need to look closely at the two theoretical accidents.

In the case of two cars of similar mass hitting head on, the primary impact will (theoretically) stop both cars dead at the point of impact. Thus the energy absorbed by each car is that determined by it's mass and a 40mph change in velocity.

In the second instance, ie one car striking another stationary one, what actually happens is that the initial impact will cause the stationary car to accelerate by half of the original impact speed. So one car slows from 80 to 40, the other accelerates from 0-40. So once again the energy absorbed by each car is that determined by it's mass and a 40mph change in velocity.

There is the added complication that in the second instance the entire mess is now travelling at 40mph, so a secondary collision and further damage is a distinct possibility. Indeed, this is where the other half of the missing energy has gone - there is now the same amount of energy still there as was dissipated in the original collision.

So whether a 80/0 head on is worse than a 40/40 head-on depends very much on what is the other side of the stationary vehicle. If it's an empty road then there isn't much difference. If there are more parked cars there then the eventual effects could double - or even worse if you consider that in the secondary collision your crumple zones might already be crumpled, so any impact is transmitted much more directly to the passengers.

This, incidentally, is a great justification for NOT stopping two feet behind the car in front when all the traffic stops on the motorway. The size of the gap you leave in front can halve or double the effects of someone running into the back of you - yet another illustration of how there is nearly always something you can do to prevent or mitigate an accident, no matter how free of "blame" you are.

Are we all in agreement now?

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

My goodness, it's like A Brief History of Time on here today!

It's all the more amazing to me then, that you you come to consider a "systems level" approach to road safety and failed to consider the central and vital issue of driver quality - and I'm talking about far more than training - these items are the fundamentals:

* driver psychology
* driver attitudes
* safety culture

Instead of wishing to improve these key components of our successful road safety system, you appear to wish to reduce the total KE in the hope that you can do so without adversely affecting these fundamentals.

Much in engineering is finding an optimal balance between competing needs. Common examples are cost/performance and cost/quality.

In this road safety debate, we shouldn't be trying to balance speed against utility or speed against safety. We should have recognised long ago that we can improve the three items in the list above with very little cost or disbenefit. We should also have recognised that there's an optimal level and style of enforcement, and if we step beyond it we should expect adverse effects on the three fundamentals.

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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 was going to reply, but JT beat me to it, saying much the same as I would have.
The kinetic energy is as I stated, it's how it's dissipated that makes the difference - and that depends on what you hit. An 80mph car hitting a stationary car will have the effect of accelerating the stationary car, and so not dissipate the full amount of KE by itself.
On the other hand, a car hitting an immovable object (such as a big tree) will dissipate all its KE.
So, putting it in a nutshell, two 40mph cars colliding will each suffer the same amount of damage as if they had hit a tree, but more than had they hit a stationary car.
But the damage to the occupants of the car (assuming no cabin invasion) is entirely dependent on the deceleration, regardless of the kinetic energy of the vehicle. So decelerating from 40 to 0 in a collision will do the same amount of damage to the occupants, regardless of whether this deceleration was caused by hitting a tree or another 40mph car.

Regards
Peter

Are you sure about that? What if I crash into a giant marshmallow at 40mph? How much damage will that do?

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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

Depends whether or not you then fall into the campfire

Hitting a 'soft' object will do less damage because the deceleration will be less. (you'll take longer to stop) But there's not much difference in deceleration whether you hit a tree or have a head-on with another similar car travelling at the same speed.

Regards
Peter