Date: Fri, 20 Nov 1998 16:14:24 -0800
Reply-To: Ari Ollikainen <Ari@OLTECO.COM>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Ari Ollikainen <Ari@OLTECO.COM>
Subject: Re: Vanagon vs Volvo Crash Photos
Content-Type: text/plain; charset="us-ascii"
At 2:45 PM 11/20/98, David-M wrote:
>There are many illogical statements in your argument.
How *many* could there be? I just wrote the following sentences
in response to your questions
DMCS>Question: Do you like high car insurance rates?
ARI> Of course not...but given the accident experience of Vanagons our
ARI> insurance rates should be MUCH lower than, say, those of Volvo
ARI> owners.
AND
DMCS>If you dont, then you should be in favour of safety regulation.
DMCS>The cost of death and injuries in vehicle collisions is astronomical.
[ NHTSA's CONCLUSION deleted ]
ARI> But of course NHTSA hasn't really offered any proof of this
ARI> assertion and the fatality rates were declining in the decade
ARI> prior to 1985-1995, as well.
ARI>
ARI> There are some interesting statistics in this particular report,
ARI> such as:
[ NHTSA's TABLE 1 deleted ]
>Two of which are:
>First, you assume that your insurance rates are based on the safety of
>your vehicle. NOT SO, they are influenced by the total costs of the
>insurance industry.
So they ARE...but NOT in a LOGICAL manner. Insurance companies
DO NOT set rates MAINLY on a particular vehicle model's loss
EXPERIENCE *UNLESS* it's EXTREMELY POOR! There are probably as many
rating systems as there are undewrwriters and actuaries at insurance
companies. Insurance companies use many different factors in
determining their rates, including, in some states, the neighborhood
of the owner, the owner's age, marital status, occupation, etc.
Many of these factors have NO correlation with risk...
HOWEVER , I was suggesting that, since the Vanagon, as a model,
has a LOW accident LOSS RATE/experience, that it should be
given a "favorable" or "good vehicle" DISCOUNT.
There's nothing ILLOGICAL about my statement EXCEPT your
INTERPRETATION!
>Secondly, you assume that because safety has improved, costs should not
>rise. The fact is that medical, legal and administrative costs are
>rising, outweighing any improcvement in vehicle safety.
>Thats why your insurance rates GO UP every year not down.
NOT mine.
>Thats why legislation that reduces accidents or the severity of
>accidents will help to keep insurance rates in check.
Like <cough> passive restraints? Five mph bumpers which were
downrated to 2mph? Or BUMPER HEIGHT standards which ONLY apply
to passenger cars...Here's something interesting to ponder, from
http://www-nrd.nhtsa.dot.gov/nrd10/aggressivity/documents/980908/980908.htm
a NHTSA paper entitled "The Aggressivity of Light Trucks and Vans
in Traffic Crashes"
<begin excerpt>
Why are LTVs more aggressive?
The preceding analysis of crash statistics has clearly demonstrated the
incompatibility between cars and LTVs in highway crashes. Still remaining
to be determined however are the design characteristics of LTVs which lead
to their incompatibility with cars. In general, crash incompatibility
arises due to the three factors:
Mass Incompatibility.
Stiffness Incompatibility
Geometric Incompatibility.
The following section will examine the relationship between LTV-car
compatibility and these sources of incompatibility.
Mass Incompatibility
LTVs are 900 pounds heavier than cars on average [5]. The conservation of
momentum in a collision places smaller vehicles at a fundamental
disadvantage when the collision partner is a heavier vehicle. As shown in
Figure 10, LTVs, as a group, tend to be heavier than passenger cars [7].
Figure 10 crossplots AM as a function of vehicle weight, and demonstrates
the strong relationship between mass and aggressivity. The mass
incompatibility between cars and LTVs appears to be growing. As shown in
Figure 11, during the time frame of 1985-1993, average mass of both cars
and LTVs has steadily increased, and the weight mismatch between the two
classes of vehicles has slowly grown as well.
[...]
Stiffness Incompatibility
As a group, LTV frontal structures are more stiff than passenger cars. LTVs
frequently use a stiff frame-rail design as opposed to the softer unibody
design favored for cars. Drawing on NHTSA New Car Assessment Program crash
test results, the linear stiffness of a selection of LTVs and cars was
estimated using the following relationship:
k = (mv2) / x2 (Eqn. 1)
where m is the mass of the vehicle, v is the initial velocity of the
vehicle, and x is the maximum dynamic crush of the vehicle. The
relationship between linear stiffness and AM is shown in Figure 12. Figure
12 indicates that stiffness is a contributing factor to the aggressivity of
a vehicle. Because the stiffness of a vehicle is also somewhat related to
its mass, as shown in Figure 13, stiffness may not prove to be as dominant
an aggressivity factor as mass. Although stiffness and mass are related in
many cases, stiffness is not totally driven by the mass of the vehicle.
Figure 13 shows that for any given mass, there is a wide distribution of
stiffness values. For example for 1750 kg vehicles, the least stiff
vehicles are passenger cars while the most stiff vehicles are LTVs.
Figure 14 compares the frontal stiffness of a Ford Taurus and a Ford Ranger
pickup. Both vehicles have approximately the same mass, but note that the
Ranger pickup is significantly stiffer than the Taurus. In a frontal
collision between the two, the bulk of the crash energy would be absorbed
by Taurus and the Taurus occupants. Far less energy would be absorbed by
the Ranger. From a compatibility perspective, a more ideal scenario would
be for the Taurus and Ranger structures to each share the crash energy
rather than forcing one of the collision partners to absorb the bulk of the
crash.
[...]
Geometric Incompatibility
LTVs, especially four-wheel drive sport utility vehicles, ride higher than
cars. This creates a mismatch in the structural load paths in frontal
impacts, and may prevent proper interaction of the two vehicle structures
in a collision. In a side impact, this imbalance in ride height allows the
LTV structure to override the car door sill, and contributes to the
intrusion of the side-impacted vehicle.
Ideally, the ride height used in an analysis of this type would be the
height of the forward-most load bearing structural member of the vehicle.
The location of this forward-most structural element however has no precise
definition, and must be estimated from other measurements. Some analyses
have used bumper height as the height of this load bearing member. However,
because in the U.S., the bumper must only meet a 2-* mile/hour bumper
impact standard, and LTVs have no bumper standard, our belief is that, with
respect to occupant protection, bumpers are largely ornamental, and their
location provides little evidence of the location of load bearing members.
The rocker panel, on the other hand, is a much more substantial structural
member, and because the rocker panel is typically lower than the
forward-most structure, serves as a superior lower bound on the location of
the frame structure.
Figure 15 shows that ride height is related somewhat with vehicle mass. For
this analysis, ride height is defined to be the rocker panel height as
measured at the trailing edge of the front wheel well [7]. However note
that the rocker panel height across all masses of passenger cars is
relatively consistent - perhaps due to the bumper standard with which all
passenger cars must comply. On the other hand, LTVs, which have no bumper
standard, exhibit a wide variation in ride height and are in general much
higher than passenger cars.
Figure 16 presents average ride height by vehicle category. Sport utility
vehicles have the highest ride height with an average rocker panel height
of 390 mm. Subcompact cars have the lowest-riding height with an average
rocker panel height of 175 mm. SUVs ride almost 200 mm higher than
mid-sized cars - a geometric incompatibility that would readily permit the
SUV to override any side structure in a car and directly strike the car
occupant.
<end excerpt.
ENJOY!
OLTECO Ari Ollikainen
P.O. BOX 3688 Networking Technology and Architecture
Stanford, CA Ari@OLTECO.com
94309-3688 415.517.3519
