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 Post subject: Appropriate speed...
PostPosted: Fri Mar 10, 2006 02:33 
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The contribution to overall risk of appropriate speed is zero

Discuss.

As a driver I believe it absolutely. So long as my speed is appropriate I will ALWAYS be able to stop in time.

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PostPosted: Fri Mar 10, 2006 02:39 
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The obvious question: is what you believe to be an appropriate speed really the appropriate speed for a given environment?


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PostPosted: Fri Mar 10, 2006 02:44 
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smeggy wrote:
The obvious question: is what you believe to be an appropriate speed really the appropriate speed for a given environment?


Sometimes not - but I'm looking for the baseline. Here it is again in different words:

If a speed causes a risk it cannot be appropriate. (now it's looking more like a definition of appropriate speed, and it's becoming axiomatic.)

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PostPosted: Fri Mar 10, 2006 03:04 
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Thinking aloud: ‘causes a risk’ could be open to interpretation.

A level of speed in itself causing a risk (cannot stop in the distance one would reasonably expect to be clear, or impeding the necessary and reasonable judgement of others (pedestrians)) is definitely inappropriate

However, we know that any speed is dangerous if someone is stupid enough, but here it’s the stupidity, not the speed, that’s causing the risk so this shouldn’t count.



How about: If a speed causes an unreasonable risk it cannot be appropriate ?

(’reasonable’ accounting for unavoidable stupidity)


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PostPosted: Fri Mar 10, 2006 03:39 
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In the event of an unforeseen problem (mechanical failure springs to mind), speed doesn''t cause risk (the failure caused it), but does exacerbate it - makes a problem more likely or more severe ramifications or both.


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PostPosted: Fri Mar 10, 2006 09:51 
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Roger wrote:
In the event of an unforeseen problem (mechanical failure springs to mind), speed doesn''t cause risk (the failure caused it), but does exacerbate it - makes a problem more likely or more severe ramifications or both.


hmm ... agree with the above.

can we have a definition of risk.. are we talking layman?.. businessman.. safety engineering?

Quote:
risk:
The possibility of suffering harm or loss; danger.


speed is energy.... the more energy.. the greater the potential harm.. and hence risk?

although if appropriate speed maybe not the greater the possibility of harm...?

in safety analysis you have a hazard with a severity.. and a likelihood..
say the hazard is 'rapid decceleration caused by collision'... the severity increases with speed.... whilst the likelihood would depend on appropriate choice of speed for the situation.

often these terms are multiplied together to grade the hazard so even if your ideal driver keeps the likelihood low at all speeds, the severity still goes up as does the overall score......

good question.


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PostPosted: Fri Mar 10, 2006 10:09 
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Just for the debate:

If I am driving at an appropriate speed I can avoid collision with reasonable and unusual situations. However, I might only be able to significantly reduce my speed if something exceptionally unusual happens.

IE: person falls out of car, or something as odd as that.

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This approach has been endorsed by Attorney General ever since 1951. CPS Code


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PostPosted: Fri Mar 10, 2006 10:52 
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Hi all,
Should we look at the risk for ALL speeds. At 0 mph is it zero risk ? At 1 mph is the risk higher. My current knowledge would say the graph of risk plotted against speed is not linear. And the graph will have a negative gradient in some places i.e. faster can be safer. Are you thinking of individual risk or would you consider 30 mph on a motorway safer for the driver (kinetic energy wise )but causing higher risk for other motorists ( tail backs rear end shunts etc )

:) Richard


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PostPosted: Fri Mar 10, 2006 12:44 
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May be we should be looking for "optimum speeds"
For a bike motorbike they are unwieldy at less than 15mph
An airplane will fall out of the sky if it goes to slow
Optimum speeds are driving within your and the cars abilities and the conditions. Fast enough to keep you attention and slow enough to react and to allow others to predict and react to you.
Also we predict what sort of traffic is in a certain type of street.
this police vanran a girl over on the wrong side of a duel carriage way at 8pm. She did not predict that traffic would be coming in the wrong direction.
I also believe that it is an issue of space and forecasting rather than "reasonable speed"

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Speed limit sign radio interview. TV Snap Unhappy
“It has never been the rule in this country – I hope it never will be - that suspected criminal offences must automatically be the subject of prosecution” He added that there should be a prosecution: “wherever it appears that the offence or the circumstances of its commission is or are of such a character that a prosecution in respect thereof is required in the public interest”
This approach has been endorsed by Attorney General ever since 1951. CPS Code


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PostPosted: Fri Mar 10, 2006 13:17 
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OK. Try this version:

The risk from appropriate speed is zero becasue if there is a risk from speed then speed cannot be truly appropriate.

I'm trying to compartmentalise the real sources of risk...

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PostPosted: Fri Mar 10, 2006 20:56 
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SafeSpeed wrote:
The risk from appropriate speed is zero becasue if there is a risk from speed then speed cannot be truly appropriate.


I can see where you're trying to go but I don't think you'll make it. Your verbal algorithm needs to be more sophisticated.

I'd venture:

"For any given combination of road and traffic conditions, there is a range of "appropriate speed". Within that range, risk does not vary relative to speed (all else being equal). In an environment that has high hazard density, that range will be narrower than in an environment that has a low hazard density or is hazard free."


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PostPosted: Fri Mar 10, 2006 22:43 
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OK. Well, let me start from yet another tack. The big risks in driving are all basic human errors. You crash because of observation, anticipation, planning, attention or judgement failures.

Given this background, is speed (a physical quantity) a risk factor at all? We know it can become a risk factor if it isn't appropriate - but when it is appropriate it's not contributing anything at all (let alone anything significant) to risk is it?

Driving has risks associated with it. Things can go wrong. But what are the true factors that create the risk and set its value? They are just human and environmental failures aren't they?

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PostPosted: Fri Mar 10, 2006 23:39 
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The more I study the subject, the more difficult I find it to see how speed can even remotely be considered to be a risk factor in most circumstances.
It can only be considered a risk factor when it starts affecting the vehicles stability / roadholding, or the drivers ability to control the path of the vehicle. But such speeds are normally well outside the envelope of normal driving on most roads most of the time.
But the speed - accident risk connection has become as rooted in the human psyche as the cold weather - common cold connection is.
They're both illusions, and even though the latter has been thoroughly disproved, even otherwise intelligent people find it difficult to tear themselves away from the concept.
It could even be said that there's a fairly close analogy between the two, in that the very thing most people do when the weather's cold and miserable - viz congregate in warm, enclosed spaces, is what causes the cold virus to be spread around.

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PostPosted: Sat Mar 11, 2006 03:04 
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I think I know what you're trying to put across, Paul.

SafeSpeed is about intelligent value-judgements of the encumbent road conditions. You know that a well-lit, straight, wide road in a rural area, in the early hours of the morning, is good for pushing on a bit and that a town centre is fraught with danger at all times. You know your car's handling characteristics and you adjust your speed accordingly.

The Government, however, base their 'safety recommendations' on the fact that the lowest IQ required to pass the Driving Test is about 80 - 20 percentile below 'average' - and the stopping distances quoted in the Highway Code as measured in 1965, using a 1500 Austin Cambridge on crossplies and drum-brakes all round.

The other problem is the application of the simple kinetic energy equation (E=1/2mv^2) which shows that a 1000kg car travelling at 10 m/s dissipates 50 kilo Newtons on impact and at 20 m/s, 200 kilo Newtons.
Whilst the physics is correct, the technology isn't. Modern tyres, brakepads, discs and ABS produce almost linear stopping up to 60 mph, above which the exponent is ^1.3 to ^1.5 rather than ^2 - a modern 1.2 Renault Clio will stop from 70 mph within the Highway Code's 40 mph figure, the car losing 15 mph in its own length.

The old 'hit me at 30mph and I'll survive' chestnut is crap - they will die. Try 'hit me braking from 30 mph' and you may be near the truth. Hitting them at 30 means you either didn't brake, or were doing 50 to start with.

Better still, go back to the 'old days' and issue every school child with their own copy of the Highway Code and re-instate the Cycling Proficiency Test.

More of them will survive and some of them may even learn to read...

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PostPosted: Sat Mar 11, 2006 10:48 
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MGBGT, Nicely spoken mate :thumbsup: . But will the government ever take that in, not on your nelly.

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PostPosted: Sat Mar 11, 2006 13:05 
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The physics have little or nothing to do with the risk of having an accident.

Kinetic energy means absolutely nothing, except if and when you actually collide with something. It does not affect your risk of having that collision one iota.
And even if and when you collide with something, your travelling speed has little or no bearing on deltaV - and its the latter, not the former, which has anything to do with the kinetic energy dissipated in the collision.

Braking distances only mean anything if and when you need to stop in a hurry. And that will only be if and when something takes you by surprise.
And the risk of something taking you by surprise has nothing to do with speed, and a lot to do with attention levels, hazard awareness etc.
Furthermore, braking distances are generally small (in most cases very small) in comparison to the distance you can actually see ahead - which, on a relatively straight road in daylight and in light traffic, is in the order of hundreds of metres. This generally gives a reasonably attentive driver plenty of time to spot hazards and potential hazards, and to adjust their speed / positioning appropriately, without having to resort to any more than a gentle to moderate degree of braking.
This means that any link between braking distances and accident risk is tenuous, at best, and practically nonexistent in the case of a reasonably attentive driver.

So, for a reasonably competent, alert and hazard-aware driver, (and I'm not talking about Schuhmachers here, most drivers fall into this category) their choice of travelling speed has little or no bearing on their risk of not being able to avoid having an accident.

On the other hand, it can be stated with at least a high degree of certainty that:

1) Inattentiveness and lack of hazard-awareness have a profound effect, both on on one's risk of not being able to avoid having an accident, and on the probability of deltaV being a high proportion of travelling speed in the event of an accident occurring.

2) In the case of most drivers, their risk of being in a collision with another road user is principally affected by the amount of time they spend in proximity to other road users - and low speeds (and low speed differentials) have the effect of increasing that time, and therefore the risk.

3) The greater the potential for two road users to come into conflict, the greater the risk of a collision occurring.

4) The less the effective visibility, the greater the potential for such conflict.
Which is why implementing measures which reduce effective visibility, such as built-up roundabouts and barrier fences, does road safety no favours.

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 Post subject: Re: Appropriate speed...
PostPosted: Sun Mar 12, 2006 01:43 
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SafeSpeed wrote:
The contribution to overall risk of appropriate speed is zero

Discuss.

As a driver I believe it absolutely. So long as my speed is appropriate I will ALWAYS be able to stop in time.


Who decides who is competent to decide for themselves what is an appropriate speed?

Is it okay for an 18 year old chav to decide if their speed is 'appropriate'?

How is this to be policed so it isn't abused by aggressive, selfish people who don't care about the consequences of their actions on others?

And finally, why do you want to speed all the time? What's the REAL issue here? (You know, the one you're trying to avoid...)

I've never sped in my life. I don't need to. I actually enjoy driving. I keep right on the speed limit, if road conditions allow. Why would I want to make my journey more stressful by driving more quickly than the road is designed for? Don't the planners know a little bit more about each individual road than I do? Like what other roads join it, the gradient, the condition of the surface, the number of accidents that have occurred there, etc.? Why would each invididual be capable of making a better decision on the maximum speed than highly trained, qualified planners with all the information above to hand?


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 Post subject: Re: Appropriate speed...
PostPosted: Sun Mar 12, 2006 03:12 
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mosis wrote:
How is this to be policed so it isn't abused by aggressive, selfish people who don't care about the consequences of their actions on others?


You'll always get people who'll abuse any system. Should we fine you from having a pint at your local just because there are a few individuals who abuse alcohol and cause mayhem?

Quote:
I've never sped in my life. I don't need to. I actually enjoy driving. I keep right on the speed limit, if road conditions allow.


And how do you know what speed conditions allow? Are you a highly trained traffic engineer?

Quote:
Don't the planners know a little bit more about each individual road than I do? Like what other roads join it, the gradient, the condition of the surface, the number of accidents that have occurred there, etc.? Why would each invididual be capable of making a better decision on the maximum speed than highly trained, qualified planners with all the information above to hand?


Yeah, right! We have thousands of miles of roads in urban areas, with wildly varying surfaces, camber, linearity, layout of junctions, spread of hazards etc etc, but they all have the self-same 30mph limit. And, equally, thousands of miles of motorway all with the same 70mph limit. And, even more ridiculously, thousands of miles of twisty single-lane country lanes, all with the same 60mph limit. All of those limits were set by an act of parliament, not by 'highly-trained, qualified planners' Incidentally, the 70mph motorway limit was imposed as a temporary measure, as a knee-jerk reaction to a number of accidents in thick fog. Three decades on, we're still stuck with the 'temporary' limit.

Tell me something, do you feel comfortable on a train hurtling through the countryside at 125mph+? Or 200mph+ on the continent? Why is that? And why is it necessary for trains to go so fast?

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 Post subject: Re: Appropriate speed...
PostPosted: Sun Mar 12, 2006 08:43 
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mosis wrote:
I've never sped in my life. I don't need to.

So, as suggested in another thread, you would be happy for speed monitoring equipment to be fitted to your vehicle and immediately surrender your licence should you commit a violation?

Quote:
I actually enjoy driving. I keep right on the speed limit, if road conditions allow. Why would I want to make my journey more stressful by driving more quickly than the road is designed for? Don't the planners know a little bit more about each individual road than I do? Like what other roads join it, the gradient, the condition of the surface, the number of accidents that have occurred there, etc.? Why would each invididual be capable of making a better decision on the maximum speed than highly trained, qualified planners with all the information above to hand?

There's a long list of roads where speed limits have been imposed by councillors that are lower than those recommended by the highly trained planners you refer to. The setting of speed limits once had some scientific basis, but increasingly this is not the case.

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 Post subject: Re: Appropriate speed...
PostPosted: Sun Mar 12, 2006 12:05 
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Pete317 wrote:
mosis wrote:
How is this to be policed so it isn't abused by aggressive, selfish people who don't care about the consequences of their actions on others?


You'll always get people who'll abuse any system. Should we fine you from having a pint at your local just because there are a few individuals who abuse alcohol and cause mayhem?


If people drink more than 10 pints, and we find that the likelihood of them committing a public order offence when in public is much larger after 10 pints than after 1 pint, then they are arrested for being 'drunk and disorderly' in public. i.e. If I was out in public and drunk, I would act normally and not ruin other people's lives, so would most likely not be arrested, even though I was drunk.
"You'll always get people who'll abuse the system". Yes, how true. Many of them are on this forum...
Why do you find it necessary to speed? Why do you feel so uncomfortable in a car travelling at the speed limit?
I seriously want to know.
Quote:

Quote:
I've never sped in my life. I don't need to. I actually enjoy driving. I keep right on the speed limit, if road conditions allow.


And how do you know what speed conditions allow? Are you a highly trained traffic engineer?


I know what speed conditions allow because I look at road signs...
And I don't find it necessary to drive really quickly all the time...
Why do you?
Try asking yourself that question, because there's SOMETHING WRONG WITH YOU.
Quote:

Quote:
Don't the planners know a little bit more about each individual road than I do? Like what other roads join it, the gradient, the condition of the surface, the number of accidents that have occurred there, etc.? Why would each invididual be capable of making a better decision on the maximum speed than highly trained, qualified planners with all the information above to hand?


Yeah, right! We have thousands of miles of roads in urban areas, with wildly varying surfaces, camber, linearity, layout of junctions, spread of hazards etc etc, but they all have the self-same 30mph limit. And, equally, thousands of miles of motorway all with the same 70mph limit. And, even more ridiculously, thousands of miles of twisty single-lane country lanes, all with the same 60mph limit. All of those limits were set by an act of parliament, not by 'highly-trained, qualified planners' Incidentally, the 70mph motorway limit was imposed as a temporary measure, as a knee-jerk reaction to a number of accidents in thick fog. Three decades on, we're still stuck with the 'temporary' limit.


Oh, it was a 'knee-jerk reaction' to accidents in thick fog, not a SOLUTION to the problem of idiots ploughing into the back of the car in front?
We're not "stuck" with the temporary limit, I'm more than happy with it. Why aren't you?
I'll tell you why - because you're a nasty, aggressive, selfish person who would happily kill somebody with your car, just because you think YOU are more important than everybody else.

I bet when you go out for a drive today you'll be fuming as usual.

Kill yourself before you kill somebody else, if you hate your life so much.
Quote:

Tell me something, do you feel comfortable on a train hurtling through the countryside at 125mph+? Or 200mph+ on the continent? Why is that? And why is it necessary for trains to go so fast?


I don't feel comfortable on a train going at 125mph, and I think it might be a slightly different environment, n'est ce pas?
It isn't necessary for trains to go so fast. People need to get a life and plan their time better.
If the price of people going fast is 3,000 people a year being killed, plus hundreds of thousands of injuries, then it's too high a price to pay.
You don't want to look at these horrific figures because, as I've said before, all you speeders care about is yourselves.

When I get my cameras installed, I'll start posting up footage of 'Mr.Angry' from Basingstoke, zooming up behind me, speeding, fuming with rage and hatred, and overtaking dangerously. After you've seen the first five hundred, will you see what I'm getting at?


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