Matthew S. Whiting

Bill Putney wrote:
>
> Dianelos Georgoudis wrote:
>
>>...Of course, the safest strategy for society would be to put an upper
>>limit to the weight of passenger cars: then we all would drive safer,
>>spend less money on cars, spend less on gas, protect others, protect
>>the environment, and be less dependent on unstable oil-producing
>>countries. Limiting the weight of vehicles is a
>>win-win-win-win-win-win proposition.
>
>
> Hmmm - that would really inconvenience people like Babs Streisand who
> goes shopping in a motor home (not just an SUV for "special" progressive
> people) so that she won't have to use public restrooms.

That is good to hear. I'd hate to think that someone of Streisand's ilk
was out contaminating public restrooms...

Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Brent P wrote:
>
>>Large passenger cars come out ahead in every type of post-crash safety
>>measure I've seen, including those that are not dependent upon driver
>>demographics. And they were also safer when those who are now old
>>and drive them were younger and driving them.
>
>
> I'm curious: Does this stuff scale linearly? By that, I mean, in two
> otherwise identical two-vehicle crashes, one crash comprised of, say a
> vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
> and the second crash with the two vehicles exactly twice (or apply any
> ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
> other crash, will the outcome statistically be the same for
> corresponding drivers and passengers of both cars in the two different
> accidents.

I may be missing a subtlety, but it should scale linearly as the
momentum scales linearly with mass.


> Another way of asking this is: If everyone in the nation became
> convinced that bigger is better and got rid of their existing vehicle
> and bought a vehicle that weighed 50% again as much as their previous
> vehicle, would the safety statistics change for multiple vehicle
> accidents (involving the now 50% heavier-across-the-board-vehicles), or
> would they stay the same?

I believe the stats would remain about the same, or improve a little as
some crashes are against moveable objects (telephone poles, sign posts,
etc.) and they would yield more readily to heavier vehicles. Obviously,
hitting a bridge abutment wouldn't be much affected by having a heavier
vehicle! :-)


Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Brent P wrote:
>
>>Large passenger cars come out ahead in every type of post-crash safety
>>measure I've seen, including those that are not dependent upon driver
>>demographics. And they were also safer when those who are now old
>>and drive them were younger and driving them.
>
>
> I'm curious: Does this stuff scale linearly? By that, I mean, in two
> otherwise identical two-vehicle crashes, one crash comprised of, say a
> vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
> and the second crash with the two vehicles exactly twice (or apply any
> ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
> other crash, will the outcome statistically be the same for
> corresponding drivers and passengers of both cars in the two different
> accidents.

I may be missing a subtlety, but it should scale linearly as the
momentum scales linearly with mass.


> Another way of asking this is: If everyone in the nation became
> convinced that bigger is better and got rid of their existing vehicle
> and bought a vehicle that weighed 50% again as much as their previous
> vehicle, would the safety statistics change for multiple vehicle
> accidents (involving the now 50% heavier-across-the-board-vehicles), or
> would they stay the same?

I believe the stats would remain about the same, or improve a little as
some crashes are against moveable objects (telephone poles, sign posts,
etc.) and they would yield more readily to heavier vehicles. Obviously,
hitting a bridge abutment wouldn't be much affected by having a heavier
vehicle! :-)


Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Brent P wrote:
>
>>Large passenger cars come out ahead in every type of post-crash safety
>>measure I've seen, including those that are not dependent upon driver
>>demographics. And they were also safer when those who are now old
>>and drive them were younger and driving them.
>
>
> I'm curious: Does this stuff scale linearly? By that, I mean, in two
> otherwise identical two-vehicle crashes, one crash comprised of, say a
> vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
> and the second crash with the two vehicles exactly twice (or apply any
> ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
> other crash, will the outcome statistically be the same for
> corresponding drivers and passengers of both cars in the two different
> accidents.

I may be missing a subtlety, but it should scale linearly as the
momentum scales linearly with mass.


> Another way of asking this is: If everyone in the nation became
> convinced that bigger is better and got rid of their existing vehicle
> and bought a vehicle that weighed 50% again as much as their previous
> vehicle, would the safety statistics change for multiple vehicle
> accidents (involving the now 50% heavier-across-the-board-vehicles), or
> would they stay the same?

I believe the stats would remain about the same, or improve a little as
some crashes are against moveable objects (telephone poles, sign posts,
etc.) and they would yield more readily to heavier vehicles. Obviously,
hitting a bridge abutment wouldn't be much affected by having a heavier
vehicle! :-)


Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Nate Nagel wrote:
>
>>Bill Putney wrote:
>>
>>
>>>... I'm curious: Does this stuff scale linearly? By that, I mean, in two
>>>otherwise identical two-vehicle crashes, one crash comprised of, say a
>>>vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
>>>and the second crash with the two vehicles exactly twice (or apply any
>>>ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
>>>other crash, will the outcome statistically be the same for
>>>corresponding drivers and passengers of both cars in the two different
>>>accidents.
>>>
>>>Another way of asking this is: If everyone in the nation became
>>>convinced that bigger is better and got rid of their existing vehicle
>>>and bought a vehicle that weighed 50% again as much as their previous
>>>vehicle, would the safety statistics change for multiple vehicle
>>>accidents (involving the now 50% heavier-across-the-board-vehicles), or
>>>would they stay the same?
>>>
>>
>>Basically, yes. An auto crash is fairly inelastic, the safety of the
>>vehicle occupants will primarily depend on how progressively the
>>vehicles crush. The amount of energy dissipated will increase
>>(dramatically) but the end result will be the same. Since energy
>>increases linearly with increased mass, it ought to scale fairly roughly
>>as you describe it.
>>
>>This is, of course, a fairly simplistic explanation and the crash
>>performance characteristics of the vehicles will be the primary factor
>>in whether the occupants walk away or not. A head-on collision between
>>two identical vehicles is essentially the same thing as a head-on crash
>>into an immovable wall at the same speed; so crash test performance is
>>the best gauge of safety in your scenario.
>
>
> Thanks for the reply.
>
> On the "two identical vehicles head-on = one vehicle into an immovable
> wall" thing, it seems self-evident that you could also extend that
> analogy and say that a heavier vehicle and a lighter vehicle head-on
> would be equivalent to the lighter vehicle hitting a wall that is moving
> at some advancing speed (i.e., more damage than head-on into a
> same-weight vehicle), and the heavier vehicle hitting a wall that is
> receding at some speed (i.e., less damage than head-on into a
> same-weight vehicle)

Yes, I believe that is correct. The speed of the advancing wall would
need to be equal to the speed of the combined wreckage of the two
vehicles, assuming they are both fused together during the crash. This
would result in the same total change in velocity for the vehicles -
from a high positive speed to a lower positive speed for the heavy
vehicle and from a high positive speed to a low negative speed for the
lighter vehicle. The acceleration experienced is equal to the change in
velocity and thus should be the same whether you hit a heavier vehicle
or a wall moving toward you assuming that the speed after impact is the
same in both cases.

Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Nate Nagel wrote:
>
>>Bill Putney wrote:
>>
>>
>>>... I'm curious: Does this stuff scale linearly? By that, I mean, in two
>>>otherwise identical two-vehicle crashes, one crash comprised of, say a
>>>vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
>>>and the second crash with the two vehicles exactly twice (or apply any
>>>ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
>>>other crash, will the outcome statistically be the same for
>>>corresponding drivers and passengers of both cars in the two different
>>>accidents.
>>>
>>>Another way of asking this is: If everyone in the nation became
>>>convinced that bigger is better and got rid of their existing vehicle
>>>and bought a vehicle that weighed 50% again as much as their previous
>>>vehicle, would the safety statistics change for multiple vehicle
>>>accidents (involving the now 50% heavier-across-the-board-vehicles), or
>>>would they stay the same?
>>>
>>
>>Basically, yes. An auto crash is fairly inelastic, the safety of the
>>vehicle occupants will primarily depend on how progressively the
>>vehicles crush. The amount of energy dissipated will increase
>>(dramatically) but the end result will be the same. Since energy
>>increases linearly with increased mass, it ought to scale fairly roughly
>>as you describe it.
>>
>>This is, of course, a fairly simplistic explanation and the crash
>>performance characteristics of the vehicles will be the primary factor
>>in whether the occupants walk away or not. A head-on collision between
>>two identical vehicles is essentially the same thing as a head-on crash
>>into an immovable wall at the same speed; so crash test performance is
>>the best gauge of safety in your scenario.
>
>
> Thanks for the reply.
>
> On the "two identical vehicles head-on = one vehicle into an immovable
> wall" thing, it seems self-evident that you could also extend that
> analogy and say that a heavier vehicle and a lighter vehicle head-on
> would be equivalent to the lighter vehicle hitting a wall that is moving
> at some advancing speed (i.e., more damage than head-on into a
> same-weight vehicle), and the heavier vehicle hitting a wall that is
> receding at some speed (i.e., less damage than head-on into a
> same-weight vehicle)

Yes, I believe that is correct. The speed of the advancing wall would
need to be equal to the speed of the combined wreckage of the two
vehicles, assuming they are both fused together during the crash. This
would result in the same total change in velocity for the vehicles -
from a high positive speed to a lower positive speed for the heavy
vehicle and from a high positive speed to a low negative speed for the
lighter vehicle. The acceleration experienced is equal to the change in
velocity and thus should be the same whether you hit a heavier vehicle
or a wall moving toward you assuming that the speed after impact is the
same in both cases.

Matt

Matthew S. Whiting

Bill Putney wrote:
>
> Nate Nagel wrote:
>
>>Bill Putney wrote:
>>
>>
>>>... I'm curious: Does this stuff scale linearly? By that, I mean, in two
>>>otherwise identical two-vehicle crashes, one crash comprised of, say a
>>>vehicle that weighs 2000 pounds and the other vehicle at 3500 pounds,
>>>and the second crash with the two vehicles exactly twice (or apply any
>>>ratio you want) as heavy (i.e., 4000 pounds and 7000 pounds as in the
>>>other crash, will the outcome statistically be the same for
>>>corresponding drivers and passengers of both cars in the two different
>>>accidents.
>>>
>>>Another way of asking this is: If everyone in the nation became
>>>convinced that bigger is better and got rid of their existing vehicle
>>>and bought a vehicle that weighed 50% again as much as their previous
>>>vehicle, would the safety statistics change for multiple vehicle
>>>accidents (involving the now 50% heavier-across-the-board-vehicles), or
>>>would they stay the same?
>>>
>>
>>Basically, yes. An auto crash is fairly inelastic, the safety of the
>>vehicle occupants will primarily depend on how progressively the
>>vehicles crush. The amount of energy dissipated will increase
>>(dramatically) but the end result will be the same. Since energy
>>increases linearly with increased mass, it ought to scale fairly roughly
>>as you describe it.
>>
>>This is, of course, a fairly simplistic explanation and the crash
>>performance characteristics of the vehicles will be the primary factor
>>in whether the occupants walk away or not. A head-on collision between
>>two identical vehicles is essentially the same thing as a head-on crash
>>into an immovable wall at the same speed; so crash test performance is
>>the best gauge of safety in your scenario.
>
>
> Thanks for the reply.
>
> On the "two identical vehicles head-on = one vehicle into an immovable
> wall" thing, it seems self-evident that you could also extend that
> analogy and say that a heavier vehicle and a lighter vehicle head-on
> would be equivalent to the lighter vehicle hitting a wall that is moving
> at some advancing speed (i.e., more damage than head-on into a
> same-weight vehicle), and the heavier vehicle hitting a wall that is
> receding at some speed (i.e., less damage than head-on into a
> same-weight vehicle)

Yes, I believe that is correct. The speed of the advancing wall would
need to be equal to the speed of the combined wreckage of the two
vehicles, assuming they are both fused together during the crash. This
would result in the same total change in velocity for the vehicles -
from a high positive speed to a lower positive speed for the heavy
vehicle and from a high positive speed to a low negative speed for the
lighter vehicle. The acceleration experienced is equal to the change in
velocity and thus should be the same whether you hit a heavier vehicle
or a wall moving toward you assuming that the speed after impact is the
same in both cases.

Matt

Chris Phillipo

In article <3F90424B.6BAE0D3@lisahorton.net>, Lisa@lisahorton.net
says...
>
>
> P e t e F a g e r l i n wrote:
> >
> > On 17 Oct 2003 08:52:47 -0700, dianelos@tecapro.com (Dianelos
> > Georgoudis) wrote:
> >
> > >If you care about your personal safety then, clearly, the best
> > >strategy is not to use a SUV but to use a mid-size or large passenger
> > >car.
> >
> > I care not only about my safety, but the safety of my family, so I
> > bought a very safe SUV.
> >
> > Go figure.
>
> Introductions seem to be in order: Pete, this is logic, Logic, this is
> Pete. Do try to keep in touch at the next car purchase time.
>

I'm sure your KIA is much safer than his Mercedes.
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Chris Phillipo

In article <3F90424B.6BAE0D3@lisahorton.net>, Lisa@lisahorton.net
says...
>
>
> P e t e F a g e r l i n wrote:
> >
> > On 17 Oct 2003 08:52:47 -0700, dianelos@tecapro.com (Dianelos
> > Georgoudis) wrote:
> >
> > >If you care about your personal safety then, clearly, the best
> > >strategy is not to use a SUV but to use a mid-size or large passenger
> > >car.
> >
> > I care not only about my safety, but the safety of my family, so I
> > bought a very safe SUV.
> >
> > Go figure.
>
> Introductions seem to be in order: Pete, this is logic, Logic, this is
> Pete. Do try to keep in touch at the next car purchase time.
>

I'm sure your KIA is much safer than his Mercedes.
--
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Remove "X" from email address to reply.

Chris Phillipo

In article <3F90424B.6BAE0D3@lisahorton.net>, Lisa@lisahorton.net
says...
>
>
> P e t e F a g e r l i n wrote:
> >
> > On 17 Oct 2003 08:52:47 -0700, dianelos@tecapro.com (Dianelos
> > Georgoudis) wrote:
> >
> > >If you care about your personal safety then, clearly, the best
> > >strategy is not to use a SUV but to use a mid-size or large passenger
> > >car.
> >
> > I care not only about my safety, but the safety of my family, so I
> > bought a very safe SUV.
> >
> > Go figure.
>
> Introductions seem to be in order: Pete, this is logic, Logic, this is
> Pete. Do try to keep in touch at the next car purchase time.
>

I'm sure your KIA is much safer than his Mercedes.
--
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Remove "X" from email address to reply.