"Large vehicles are generally designed to be
    stiffer and have less crumple zone protection."

I would think that this would not be the case,
rather, I would think that adequate 'crumple'
would be engineered in and would further more be
proportional 'crumple' per the vehicles weight
*yet* providng for the same amount of personnel
safety, as the Institute for Highway Safety (a
'cover', BTW, for an insurance lobby!) tests 'crumple
zones' and resultant effects on passengers by running
vehicles into concrete abutments and *not* other
vehicles ...

(Discussion above was assumed above to involve only
 passenger vehicles and not commercial vehicles/trucks/
 buses which don't seem to be required to meet the same
 requirements for 'crumple' as passenger vehicles.)

RF Jim

----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, August 25, 2002 3:49 PM
Subject: Re: [OT]: Gas & taxes (was Online electronics store)


> > There was an amazing interview shown here last week involving
> a Washington DC lobbyist for the "right to drive
> huge gas-guzzlers" campaign, who was adamant that lighter cars are
> inherently more dangerous in an accident, and even went as far as to say
> that with a car with 4 people in it versus the same car with 2 people, the
> 2-people would be injured more because their car was lighter...
>
> "Ya canna' change the laws of physics, Captain!"  - unless you're a
> politician, apparently!
> >>
>
> The laws of Physics are slightly on his side in the altter case,
> unfortunately. While the momentum change for both "vehicle systems" is
> liable to be about the same the VELOCITY PROFILE for each vehicle will be
> different. Take it to its extreme case and then look at the 2 and 4 person
> case. A large heavily truck travelling at high speed impacting a small car
> travelling at low speed will only slow slightly whereas the car will
> suddenly assume a high velocoity in the reverse direction. The momentum
> change for both will be the same. A person in each vehicle will have their
> personal momentum (which is what concerns them) altered quite differently
in
> each case. The occupants' personal change in velocity is what matters to
> them and their relative vehiclemass will have a bearing on this.
>
> Taking the 2 person / 4 person case, the vehicle with the greatest MV
treats
> its passengers best *all other things being equal*. The important point to
> note is all other things are not equal. Large vehicles are generally
> designed to be stiffer and have less crumple zone protection. A 4Wd
vehicle
> will generally not 'fold up" in an accident the same way that a car
designed
> to do so will do so. The subsequent difference in peak acceleration forces
> can have a significant effect on outcomes - which is why crumple zones
> exist.
>
>
>         RM
>

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