Safe Speed Forums

I'll try and make myself clearer this time. Pick up a book on "Risk" even the most simple one and you'll find the following:

Event Loss (values between 0 and 1) = Event Probability x Event Severity

For "Event" you can substitute "Default" (if you are a bond analyst), "Insurance" (if you are an actuary) or even "Accident" if you're a reader on this forum.

or put as Superman says to Lois Lane "Statistically speaking air travel is still the safest form of travel".

Well how about the fact that an aircrash has an Event Severity of near enough 100% (i.e. not many people walk away from such a catastrophe). However, compared to car travel the very low level of "Event Probability" more than compensates for aircraft's very high level of "Event Severity", thus giving a lower "Event Loss" than car travel.

Why is that, well plane travel is more or less in a controlled environment, with Air Traffic Management. Whilst I'm not an expect on aircraft separation distances, a quick check on Google suggests they are about 8km apart at cruising altitude. Assuming they are travelling at about 1000 km/h (about 10x a motorway driver), to get to similar levels of safety on a motorway would require 800m separation between cars.

Now I've done the maths, you go and figure the following:

What does speed to do Event Probability for a car driver (I'll give you a hint, think about reaction time).

What does speed do for Event Severity (another hint, why is debris from and aircraft accident spread over kms and not metres (as with cars).

Which is more dangerous two cars colliding head on at a combined speed of 120mph or a moving car hitting a stationary car at 120mph (i'll give you a hint, think conservation of momentum)

It sounds like you are getting obsessed with theory and ignoring the facts.

Road safety is a much more complex issue where concentration, seperation, visibility etc play a much more significant role.

Does slower traffic result in fewer accidents? If you do not have the answer then there is no point in continuing to bang the drum.

If you try and make the facts to fit the theory then you have lost the plot. The problem is there are too many stake holders that want speed to remain the main thrust of road safety. Thats why our roads are getting more dangerous.

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Speed camera policy Kills

Please correct me if I am wrong but I thought most children killed by cars pedestrians at the time of the accident.

If so why can you say driving at a Safe Speed on the motorway Irrelevant to whether it is within the legal limit or not affect the number of children killed?

Wouldn’t the money time and effort spent on speed cameras be better spent on educating? The children to the dangers of the roads

Wouldn’t it be a better idea to remove crap clutter from the sides of roads that hide children from car and cars from children? Instead of adding clutter or “calming” as it is now known.

And if you really wanted to drop the number of people killed on the roads wouldn’t it be better to improve all aspects of driving including observation and anticipation so we can reduce the number of accident from happening in the first place rather than hopping that the accidents that do happen will not kill people.

And wouldn’t it be nice if we had a well resourced extremely knowledgeable experienced professional body of men and women that could patrol all the nations roads target Dangerous drivers (you know the ones that kill people) and get them of the roads while at the same time been able to help out inexperienced or lapsing drivers with a few words of wisdom.

We had something like that once before I wonder what happened to it.

It's actually absurd to suggest that road safety is primarilly subservient to the physics of the situation. We're not talking about bowling balls - each and every vehicle contains an individual actively attempting to manage the risk. We covered this yesterday, but you ignored it. Please don't ignore it again. Try these figures:

32 million drivers, 3,500 annual road deaths.

1 death per 9,000 years of holding a driving licence.

The physics can't bite until a driver makes a mistake. It's the mistake rates we have to concentrate on.

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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

...then this one came along!!!





Okay, lets agree on the fact that insurance companies' are designed to maximum return to shareholders either in the form of "reducing claim rates" or increasing "premia".

Let's further suppose (just hypothetically) that the insurance companes of the US have clubbed together and come up with a website:

http://www.highwaysafety.org/

...that is a hotbed of propaganda. Not content with spreading such well known disinformation along the lines of (i) alcohol and driving don't mix (ii) younger drivers are more risk prone and (iii) motorcycle helmets reduce severity of injury, one afternoon, in an effort to maximum shareholder profit, they come up with the grand-daddy lie of all time "increasing speeds beyond 65 mph will giver rise to more accidents"!

Now just suppose that you are correct that the IIHS is brainwashing everyone to maximise profit - what you're suggesting from your post, is the truth is the complete opposite (i.e. actually going faster is will reduce risk of claims). Why do you think that this "truth" has never been outed? Is there some great "lone-gunman" cover up that you want to tell the world about?

Does it ever occur to you, rather than engaging in this modern day equivalent of the "flat earth society", that the powers that be (including the German Autobahn regulators) all might correct in thinking "speeding on motorways is dangerous".

The whole case of the self-styled 'SafeSpeed' campaigners depends on making road safety into an incomprehensibly complex process, so that they can hide their real purpose - they like driving fast, but they hate getting caught!

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I stole this .sig

Even this formula is not that simple.

Assuming that we are restricting the case here to "driver avoidable" accidents, can we agree that our "Event Probability" therefore largely comprises "driver response". Ie how the driver responds to a potential accident scenario is the major determinant of accident probability. This si almost impossible to correlate to numerical speed.

So how do we determine "Event Severity"? From a physics point of view this is surely proportional to "expended momentum", which we can then break down as "mass x impact speed".

So what determines impact speed? If we fix the environmental conditions (we can't really but without some assumptions this goes nowhere) then it's down to something like "travelling speed differential x driver response factor x reaction time factor"

In other words, how the driver responds, and how much time he has to respond, will have as much effect on the final impact severity as his initial speed. If we feed this back into the original equation we find that travelling speed is just one of many factors, yet driver response (expertise, alertness, attitude, what have you) affects BOTH primary factors.

This echoes my earlier question: ie what does this tell us about the priorities we should be assigning to road policing?

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

what about when driver's don't make "a mistake" but an encounters an event through no fault of his own:

Here are a few examples, I've come across on UK motorways

- a Renault 5 sitting in L3 with its headlights facing me
- the remains of an HGV blowout in my path about 1m in length
- the bonnet of a Morris Minor coming off its hinges and landing right in front of me.

Help me understand why going at 100mph rather than 70 mph is going to be safer - I just can't see the light!

In a way, you've nearly answered your own question!

Look at it this way:

In order to avoid the large chunk of tyre debris in L3 which is most important - adhering to the 70mph limit, or keeping a safe following distance, an awareness of potential escape routes, and good observation of the road ahead?

Suddenly, the speed thing doesn't seem quite so important...

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

lets us all hold hands and sing songs of praise for these words of wisdom.


From a country with just about the worst road safety record going

Just in case you don’t get it the first line is sarcasm.

Only if measured in terms of distance travelled. If measured by the number of journeys, it's a completely different story. (hint: we always intend completing a journey when we start out, whether it's in a car or plane, whether it's 1 mile or 10,000 miles)



..er, shouldn't you be squaring the ratio of speeds?



How does that work then?

Cheers
Peter

I have also faced these instances I drive 1000 miles a week mostly on motorways. If you have the correct seperation with other traffic they are not an issue. The faster you drive the greater the separation. The lower the risk. The most dangerous situation is 60mph traffic nose to tail which is what we sometimes get now. There is no time to react. Give me a clear lane anyday.

BTW have we finished with the laws of physics now. Can we talk about road safety for a change.

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Speed camera policy Kills

Agreed, but my purpose was to illustrate a point rather than advocate the merits of air travel, I subject I would score "D-" on.



Well I had in mind that Event Probability was a function of reaction time (t) and my rusty physics suggested that t = distance/velocity. For a given distance, increasing your speed (v) will reduce your reaction time - what equation were you working from?

EB

...and I thought "increased seperation due to increased speeds" was risk neutral.

Well you learn something new everyday.

That's libellous. Behave yourself.

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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

JT, you're absolutely correct (no scarcasm intended). However, the only difference between my opinion and yours is that in real world driving, safer following distances leads to "risk mitigation" and not "risk elimination".

Accidents do happen with the best trained drivers on the road (e.g. Traffic Cops). That's because, as you guys keep on pointing out, we live and drive in a complex system. When they do happen, the accident severity is directly correlated to velocity (squared).

Now, if you and your colleagues, believe that by driving faster (albeit with safe separation distances) can lead to lower accident probabilities - in fact so much lower as to reduce the effect of increased accident severities - then that is a matter of conjecture.

IMHO, I contend that driving faster, whilst reducing the window of accident opportunity in an overtaking situation, results in the increased risk of accident through reduced reaction times for unavoidable events (Renault 5s, HGV tyre debris and Morris Minor bonnet's) taken together with increased accident severities.

I never set out to win you guys over, I'm more interested in whether your arguments stand up and ultimately that's a matter of opinion.

Do you believe FOREST, the association of tobacco companies too?

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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

The point here seems to be that driving, particularly at speed, involves a package of skills which are quite well interwoven.
Yes, if you travel at 100mph affording your driving the space, time and attention demanded at 70 mph, you are almost bound to give yourself little time to react if something unexpected happens ahead. Driving at 100mph on a UK motorway can be accomplished quite safely providing the driver accomodates changing circumstances.
Unfortunately our perception of 'speeding' on UK motorways is soiled by mental images of those we've witnessed not giving sufficient allowance for other traffic etc.

We're not trying to get people to drive faster. We're trying to get the government to help people to set their speed for the right reasons. The number on the speedo turns out to be a hinderance rather than an assistance.

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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, since its you, I'll give you the time your position deserves. See if you can do the same with my question regarding the assertion one of your members made that "the IIHS is conflicted".

No, in the case of FOREST, I would be extremely sceptical of their claims.

Why - although I can't be sure, I can see that the tobacco companies have a vested interest in replenishing the market with new smokers that have otherwise been removed as a result of their product. To that end, their track-record in terms denying the dangers of tobacco and the addition of nicotine, would lead me to be cynical.

Now getting back to the IIHS. If somebody can back up this statement of "They are arch twisters-of-fact and should not even remotely be trusted.", I'd be grateful. Maybe I've been living in a vacuum for my adult life as I'm ignorant of what lies these "twisters of fact" have peddled.

Answers please!