Safe Speed Forums

I have clashed with people all over the internet because I usually argue FOR the "speed kills" stance.

I do understand that "speed" in context can be quite safe and I do understand that some people can drive fast and be very safe while some people can drive slowly and be a hazard to everybody.

Road conditions and the differing speeds of differing styles and types of vehicle can contribute to accident just as much as speed itself can.

I have heard almost all of the arguments against the "speed kills" stance and I STILL feel that speed under almost all conditions is more dangerous than slowness in general.

"Explain yourself"...I hear you say.

OK...then: My argument is really quite simple....

When a vehicle is travelling at speed it has (X) amount of kinetic energy stored in it's body. The faster it goes the more kinetic energy increases pro-rata to the ground speed in the vehicle.

The slower the vehicle goes the smaller the amount of kinetic energy relative to the speed of the vehicle is stored in the vehicle.

As kinetic energy can only be dissipated by the brakes and the friction with the tyres on the roads it can only be returned to the road very slowly in safety.

The other way to dissipate kinetic energy is via the sudden stop that results in the event of a crash or a body hitting the vehicle. This body can be from the size and weight of a human-being to the size and weight of an immovable concrete bridge pier.

If the kinetic energy absorber is a human being or an animal then very little of the stored energy in the behicle will be required to destroy or severely damage the body. If the kinetic energy absorber is a concrete bridge pier then all of the stored energy will be dissipated into the pier and in turn the vehicle and it's occupants will be severely damaged or destroyed.

The more road-speed that is being attained by the vehicle the more this road-speed will contribute to the stored kinetic energy in that vehicle and pro-rata to the roadspeed the more kinetic energy will need to be slowly or explosively released via friction or sudden stop.

ERGO... the faster you go the greater chance you have of being destroyed by that speed when that kinetic energy is released.

SPEED KILLS.......and greater speed kills with greater efficiency !

_________________
Regards

Papaumau

http://www.rip-off.co.uk/index1.htm
http://www.network54.com/hide/forum/100558

You only need one thing to cause an accident. DRIVER ERROR. Speed only relates to the extent of the damage.
We can be killed from a 30 MPH impact, which is generally our lowest speed limit.
You are carrying this false notion that if you drive within the speed limit you are safe. You are fooling yourself, in order to avoid deaths on our roads we need to remove accidents.

At present, it is completly acceptable to be involved in a traffic accident. Unless you kill/ severly injure someone, you will not face prosecution in the UK.

Accidents generally happen below the speed limit. The speed limit may not be the appropriate speed to be traveling at. A 30 MPH Limit in bad weather conditions is not safe. However that same stretch of road in dry clear conditions is completly safe for 30 or 40 MPH.

It all comes down to how Speed is used.

The largest Percentage of accidents are down to drivers turning Right across traffic. This is driver error and has nothing to do with speed, the driver making the turn has not read the road or approaching traffic correctly.

Driver error Kills, based on the simple facts. A vehicle moves into the path of another causing an impact. The result of how much damage is done is down to simply when the other vehicle spotted the hazard and how much speed was reduced before impact.
It is impossible to establish how much reaction time we have, as this is down to how bad the error being made ie: how close the vehicle is to the other.

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Steve

Much of the 300,000 word Safe Speed web site concerns the relationship between speed and safety. Boiling the huge complexity of the subject down to two words: "speed kills" is dangerous and misleading.

I agree that more speed means more kinetic energy and that more kinetic energy at impact means more damage.

But speeding isn't king whe it comes to causing accidents. We simply don't have many accidents that are caused by "normal motorists" exceeding a speed limit.

Inappropriate speed is highly dangerous both above and below the speed limit. Avon and Somerset data tells us that 2/3rds of excessive speed accidents take place entirely within the speed limit.

So in essence, the Safe Speed proposition is that overemphasizing the importance of speed limits can lead to more inappropriate speeds. One mechanism is that a driver will plough on into danger at 29mph convinced by the propaganda that his speed must be safe. Another mechanism is that drivers are distracted by speed enforcement - they look at their speedos more and they look out for cameras more - and this means that they react later to hazards.

I recommend careful consideration of these Safe Speed pages:

http://www.safespeed.org.uk/tiger.html
http://www.safespeed.org.uk/lie.html
http://www.safespeed.org.uk/inattention.html
http://www.safespeed.org.uk/roadsafety.html
http://www.safespeed.org.uk/background.html
http://www.safespeed.org.uk/fatality.html
http://www.safespeed.org.uk/effects.html

I'll be more than pleased to answer any questions or listen to any arguments. All reasoned debate is welcome here.

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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 you say is correct as far as it goes, but makes no allowance for avoiding action. What if the kinetic energy is released by safely braking to a halt? Or by steering round the danger, in which case the energy isn't released at all.

Taking your example of a car hitting a concrete bridge pier, there is no argument that the driver will suffer much greater injuries if he collides with the pier at 60mph than he would at 30mph. Scaling things up a bit, air travel must therefore be considered inherently dangerous due to the lethal effects of several hundred tons of airliner hitting a mountain at 500 knots or so. However, in the real world both pilots and drivers take avoiding action. The pilot's ability to avoid the mountain depends on seeing it in time to steer round it or over it. Since mountains appear on maps the pilot will know about the mountain even before take-off. Airspeed in the vicinity of the mountain is largely irrelevant when it comes to avoiding a crash, although it is highly important if things go wrong and a crash actually takes place.

The same thing applies to me driving towards a concrete bridge pier. Whether I'm doing 30 or 60 in the vicinity of the pier only becomes relevant if I fail to notice the pier in time to avoid hitting it. On roads I know well I have advance knowledge of all the fixed hazards like concrete bridge piers, as well as knowledge of where occasional hazards such as pedestrians are. On roads that are unfamiliar I would drive more conservatively, although I can infer many things from the characteristics of a road. For example, all the bridge piers on the motorways I know are on either side of the carriageways and often in the central reservation as well. Although I've never been on the M8 I'd expect the same to apply there, so I can safely drive at the same speed on the M8 as the locals without hitting any bridges.

If we're talking about colliding with a pedestrian, then both parties have an opportunity to notice the other and take avoiding action. For example, if I want to cross the road and you're driving towards me, you have the opportunity to see me and react by braking, and I have the opportunity of seeing you and react by not crossing the road yet. As far as any injury to me goes, your speed became irrelevant when the collision was avoided. It would only have been a a factor if you were driving so fast that you could not brake in time and I could not see you until it was too late. Even then in many instances it could be said that I caused the collision by failing to observe properly before I began to cross the road. This is what happens in reality. People avoid collisions far more often than they fail to avoid them.

Perhaps it's the way I read your post, but it seems that you want to treat symptoms rather than causes. In other words, if we reduce all vehicle speeds then we reduce the number of life threatening injuries. As I said above, this is true as far as it goes but begs the question of how far we should reduce speed. Why stop at 30 mph? Why not make it walking pace? A galloping horse could inflict a lethal injury, so should horse riding be banned too? I'm sure you'd agree that this is taking things to a silly extreme, since it makes the rather pessimistic assumption that collisions are inevitable so steps should be taken to minimize the consequences. In reality virtually all collisions are avoidable. The driver can brake, the pedestrian can choose not to cross at that time, the pilot can fly around the mountain. Even in the event of a car crash due to mechanical failure we should ask if the car was properly maintained. Even if it was there may be still be a human cause further up the chain if the component that failed wasn't subject to adequate quality control. About the only situation that readily springs to mind where no human fault could possibly be found is if a driver lost control and spun off the road during an earthquake. However, is it really appropriate to drive everywhere at an arbitrarily low speed in case of an earthquake causing us to lose control and possibly hit another road user? Even if parts of the world that are prone to earthquakes this is not seen as a realistic option.

We'd probably both agree that one avoidable road death is one too many. Where we differ is that I would prefer that death was avoided by preventing the accident, not by merely reducing the severity of the injuries to a survivable level.

Except there's absolutely no evidence of reductions in accident severity in the speed camera era - and we've had a decade for the benefit to start to show.

In fact the opposite is true. Accident severities appear to be increasing.

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

This may be due to distortion in the serious injury figures:

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

Whever way you look at it, accident severities are not reducing.

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

Thanks for your responses to the threadstart...

I agree with all that both of you say. I particularly agree with the point that it is driver mistake that causes most accidents. I even agree that it is the right-turn maneouver that is responsible for most accidents.

ALL TRUE !

I STILL stand by the slogan "speed kills" as quite simply it does if the situation arises where it is allowed to.

The fact that as we get down to and below thirty MPH speed then comes less and less into the equation is also true. Why is it true ? It is true because at that speed, (once again allowing for good or bad road conditions ), the stored kinetic energy can be transferred to the road more easily and more slowly before some of what is left of that energy is then directed into the body of the object that is in the way of the vehicle concerned.

At speeds above and greatly above thirty MPH the times required for reacting to any given situation are reduced pro-rata to the speed of the vehicle, therefore any potential accident situation is exacerbated by the speed of the vehicle and not in any way reduced.

The very common equation of thinking distances and moving distances is DIRECTLY related to the speed of the vehicle.

It is THESE points that have been ignored by the people who dismiss the "speed kills" argument.

I have been willing and eager to agree about the reasons for accidents and I will be very happy when I find one of these persons above that will admit that "speed" is a significant factor in the SERIOUSNESS of the results of any such accident.

_________________
Regards

Papaumau

http://www.rip-off.co.uk/index1.htm
http://www.network54.com/hide/forum/100558

It's been mentioned that you're more likely to be concentrating harder at higher speeds. This can have a large effect on 'thinking distance'.



Yes, the speed of the impact has a very simple connection with how much damage is done to the object (person!?) collided with. However, the speed of the impact is not DIRECTLY related to the speed the car was driving at shortly before the accident! You may find that hard to believe, but there is a LOT of evidence for this - again it comes down to the concentration issue, amongst other things.

No one is trying to say that driving at 60mph through a town centre is sensible. But as Paul is fond of saying, very few accidents happen suddenly/immediately. A skilled driver is able to better anticipate and react to events unfolding on the road ahead than a comparatively unskilled driver. A skilled driver is one who constantly adjusts his speed based on what is around him - exceeding the speed limit when it is safe to do so, and driving far under it when it is not safe to go as fast as the speed limit. An unskilled driver is one who sticks blindly to the speed limit in the belief that they are safe.

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-mike[F]
Caught in the rush of the crowd, lost in a wall of sound..

Speed ISN'T a significant factor in the seriousness of accidents. Try this:

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

There simply aren't enough cases of high severity accidents - we have many millions of "speeding drivers" each day but only about 7 fatal accidents in total.

And try this:

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

You cannot create the "log" scale of accident severity with a physics model. You can only create it with a psychological model of accident causation. The largest influence on accident severity is "degree of driver error". Free travelling speed plays a very minor role. If it didn't we'd be killing many thousands each and every day.

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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

Kinetic energy equals 0.5 times mass times the square of velocity.
Therefore, a 10-ton bus moving at 10mph has as much kinetic energy as a 1-ton car moving at 30mph (approx)
So why don't we limit buses to 10mph in 30mph areas?

Just a question

Regards
Peter

What's so magic about 30mph? Surely one could use the same argument for 10mph? Or 5mph? Or 50mph?
In any case, that argument is a bit thin. The time required for reacting to any given situation is reduced by approximately one-eighth of a second for every additional 5mph. You cannot blink that quickly.



You've left out a very important factor - the laws of probability. The probability of being within any given distance at any given time is directly proportional to the time taken to cover that distance, that is, inversely proportional to speed. Therefore thinking time is what matters, not thinking distance. And thinking time is totally independent of speed.

Regards
Peter

And if such a situation does not arise speed does not kill, nor does it maim or injure. The question is how often the situation arises. Pretty rarely compared to the number of miles travelled daily by all UK vehicles. We could rephrase your position by saying "Speed occasionally kills, usually after something else has gone wrong".
You're still making the assumption that collisions are inevitable. I'm sorry but I believe that this attitude is defeatist. Collisions are almost all preventable, and if we can collectively get better at prevention then impact speeds are meaningless. Imagine for a moment that we had a whole decade in which no collisions happened - would anybody even be discussing collision speeds in the absence of any collisions? I know eliminating all collisions is going to be unrealistic without actually banning all motor transport and making us all walk everywhere in Zorbs. But in reality we can still make improvements towards this ideal by improving roads and road users.
That's a matter of space as well as time. Reaction time is almost a non-issue given sufficient space in which to react, simply because the available time goes up as well. If you're leaving only 20 feet or so at 30mph then you've failed to give yourself time to react. If it's closer to 200 feet then you've given yourself much more time. You also have to rely on other road users to behave sensibly. For example, the time and space you have given yourself is restricted if I walk out into the road from behind a bush. But in that case I have prevented you from reacting in time.
True, but how is relevant for a driver who takes account of this and maintains a safe distance for the situation?
Then I must have already made you very happy. After all, I did agree earlier that impact speed greatly affects the outcome of collisions. However, as potential collisions may number in the millions each day and actual collisions are relatively rare, I still believe that we are not getting to the heart of the matter. Look at it like this, gunshot wounds are pretty nasty and there's plenty of illegal firearms kicking about. Imagine I have the power to grant you a single wish. Would you prefer me to get rid of all the guns, or to give everyone a flak jacket? It's the same thing with road safety. Do you want to prevent collisions or cure their results? If it's prevention then we can move on to arguing about the best way of doing that, 'cos I don't think cameras are helping.

I'd like to expand somewhat on Gatsobait's main point.

Let's think for a moment about how many potential accidents our "road safety system" (whatever that is - more below) avoids in a day.

Suppose tomorrow at midday every driver in the land shut their eyes for just 20 seconds. How many crashes would there be? How many fatalities?

Let's make a wild guess - 24 million cars, 2 million of them on the road. Half of them crash - 1 million crashes. For every million crashes at present we have about 1,000 fatalities, so let's say that by half past 12 there will be about 1,000 deaths.

But in the real world drivers go about 7 years on average between crashes. They never shut their eyes for 20 seconds.

The road safety system that avoids total carnage is drivers reacting to hazards. Not much more and not much less. These reactions are far more precious than a few mph over or under the speed limit.

The big bother with "speed kills" road safety philosophy is that it comes with side effects. when we force drivers to slow down they are less attentive. When we threaten to take away their licences for speeding they watch the speedo more. When we use cameras drivers look out for them even when they are not there.

These side effects intefere with our basic road safety system and we shouldn't be surprised if accidents and accident severity increase as a consequence.

The good news is that our drivers are very far from the ideal and they could be so much more effective at avoiding accidents. This is the message of hope - we have masses of room for improvement despite having the safest roads in the world already.

Finally, try this thought experiment. We're going to estimate the impact speed of an average incident. According to research, near misses outnumber accidents by between 5:1 and 30:1. Let's take a middle 10:1 estimate. Ten incidents. One crash at free travelling speed. Average impact speed one tenth of free travelling speed. This gives a real clue to what's actually happening in the real world.

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

YES IT IS!

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It's Champion Man

The number of fatalities would be proportional to the average speed.

As speed increases, so does fatalities. This is the indisputable fact that the thread was opened with.

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It's Champion Man

By the number of times my words have been quoted in the replies above I would imagine that I have maybe put the cat among the pigeons by my stance on the "speed kills" slogan !

Of course, I have read all of those sensible arguments before and most of them are irrefutable. The trouble is that all of these arguments go towards the reverse of the slogan, and therefore try to say that "speed does not kill". The reverse of the slogan is just as nonsensical as the slogan itself - out of context

This would suggest to me that the people who like to drive fast want to keep doing it at any cost. Fair enough, that is only being human I suppose.

I do not have the time to respond to all of your points, but I will try to discuss some of them....

It seems to be accepted that the faster you go the better your concentration is and because of this idea the better your thinking times and reaction times are.

I would refute this as in most of today's very fast and comfortable cars it is very easy to get relaxed and even fall into a stupor when one is cruising down a motorway. The use of a cruise-control system makes this phenomenon even more severe if you let it. Driving slowly may contribute to inattention if your journey has been a tiring one and here the attention and the thinking and reaction times and distances are pro-rata to your tiredness. This goes without saying really !

Nevertheless, if you are tired and you are travelling at high speed your good OR bad thinking and reaction times are directly related to the distance that you travel during these important seconds or parts of seconds. This distance has been said above to be able to allow the driver to avoid collision, but the actuality is that the faster you go the harder it is to change direction or to avoid a collision. In fact at high roadspeeds the attempt to change direction can actually contribute to the accident itself.

If the concentration has been bad enough due to tiredness at slower speed the accident that results will be developed pro-rata to the speed that you were travelling at the point of impact

Of course, as someone above said...."Free speed however high does not contribute to the seriousness of an accident" - or words to that effect, because while the vehicle, a car, a boat, a plane, a missile even, while passing through the air at speed does no harm while it is engaged in that speed. Not until it stops. At which point the speed at the point of impact MUST contribute to the level of destruction that results in the stopping.

I am sure that most of you will agree that this thesis suggests that as long as the road or the air is clear that as long as the vehicle is under control, the speed itself is unimportant. As our roads and even our airspace is now becoming more and more crowded the chance of any vehicle finding totally clear airspace or roadspace becomes less and less as it covers the distance that it needs to cover on it's journey.

As the clear airspace or roadspace becomes less and less the speed at which you cross that available space increases the chances that you will meet one of your fellow travellers crossing that space. When you DO meet one of your fellow travellers you will want to ensure that you do so at the slowest speed that is possible. It is during the desire to reduce speed from fast to slow that the stored kinetic energy will be released and if that energy is not dissipated in a controlled way either you will lose control of your vehicle or you will get rid of that energy very quickly when you either meet one of your fellow travellers head-on or you come up against an immovable object.

To the person that lectured me about the relationships with mass and speed and inertia and kinetic energy storage....thankyou, but I am already aware of this information. Knowing these indisputable facts does not change the equation about speed being a vital factor.

_________________
Regards

Papaumau

http://www.rip-off.co.uk/index1.htm
http://www.network54.com/hide/forum/100558

Actually, once we have taken driver response out of the equation, we could expect fatalities to be approximately proportional to the 4th power of speed.



Of course! That must be why motorways - (the fastest roads) have more fatalities than town roads (the slowest roads). Except they don't do they? It's the other way round. There must be more to it...

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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

You snipped this URL:

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

Perhaps you would like to try to find the flaw in the proof?

Or shall we play pantomime games instead?

OH NO IT ISN'T.

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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

Hardly. You show no sign of considering the arguments in proper detail.



No. The argument is that there are nowhere near enough high severity accidents in the real world to indicate that free travelling speed plays a significant role in accident outcomes.

See this page:
http://www.safespeed.org.uk/proof.html

***

Ashton and Mackay 1979 (frequently quoted by government) tells us that in a 30mph impact 50% of pedestrians will die. We believe it. It's good research.

But the real world figures seem to tell a completely different story. Child pedestrians, 2002, built up areas:

Injuries: 14,000
Deaths: 58
Percentage of deaths: 0.42%
Source: DfT

And we know that 59% of cars were exceeding the 30mph speed limit at sample sites. (source: DfT)

So why didn't 7,000+ die

What saved 6,942+

if speed didn't kill 7000+, what makes you think it might have killed the 58

Please make sense of this before we continue

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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

You're missing the point entirely.
It's only the impact speed that's a significant factor in the seriousness of accidents. But there's no relationship between pre-incident travelling speed and impact speed unless the driver does not react before the impact. In the vast majority of collisions, the impact speed is very much less than the travelling speed - thanks to driver reaction.
Improving driver attention levels has far more of a safety benefit than tinkering around with speed limits will ever have.

Regards
Peter

Your sum is missing some important evidence.

A vehicle is completly safe at its designed speed, if it is used correctly.

No vehicle is safe, when a driver makes an error.

So if you remove the driver error, all speed is safe.

So your lecturer forgot to give you an important summary.

<<At speeds above and greatly above thirty MPH the times required for reacting to any given situation are reduced pro-rata to the speed of the vehicle>>

Incorrect, a 30 MPH speed limit is put in place due to the restrictions in place on the road layout reducing reaction time.

Most 30 MPH limits (built up areas) give you next to no reaction time.

A 70 mph limit, gives us ample reaction time.

Simple facts which you left out of your kinetic system.

Driving between houses, reduces your hazard perception time to under 10 sec.

Driving down straight open roads, allows you more like 30 sec reaction time.

So you are more likley to be involved in an accident in a built up area whilst traveling within the 30 mph speed limit, than your are traveling at 70 mph on a motorway.

_________________
Steve