making sense of crash test results

[Anonymous]

In my search for the safest car, I have been struggling over tons and tons
of data on automotive safety and crash tests and am confused about a lot
of things. Here's one example:

The National Highway Traffic Safety Administration (NHTSA) crash tested
both the Toyota Rav4 and the Toyota 4Runner in 1998. The probability of
driver and passenger injury have been estimated by them in a FRONTAL
crash as follows:

Prob of driver injury P. of passenger injury Restraint used

Rav4 13% 11% belt+airbag
4Runner 24% 25% belt+airbag

Now the Rav4 is a much smaller vehicle with curb weight 2990 lbs, length
163 in, width 67 in, wheelbase 95 in made by Toyota. The 4Runner is much
larger and tougher, also made by Toyota, with curb weight 4010 lbs, length
179 in, width 67 in, wheelbase 105 in. Just compare their weights:

Rav4 as tested: 2990 lbs
4Runner : 4010 lbs

What I do not understand is why the NHTSA would estimate the probability
of driver/passenger injury to be twice as high in the 4Runner as compared
to the Rav4 in a frontal collision. If anything, it should be the
other way round. Could someone please help?

Jim Baluta

[Stephen H. Westin]

Anonymous <nob...@replay.com> writes:

> The National Highway Traffic Safety Administration (NHTSA) crash tested
> both the Toyota Rav4 and the Toyota 4Runner in 1998. The probability of
> driver and passenger injury have been estimated by them in a FRONTAL
> crash as follows:
>
> Prob of driver injury P. of passenger injury Restraint used
>
> Rav4 13% 11% belt+airbag
> 4Runner 24% 25% belt+airbag
>
> Now the Rav4 is a much smaller vehicle with curb weight 2990 lbs, length
> 163 in, width 67 in, wheelbase 95 in made by Toyota. The 4Runner is much
> larger and tougher, also made by Toyota, with curb weight 4010 lbs, length
> 179 in, width 67 in, wheelbase 105 in. Just compare their weights:

<snip>

> What I do not understand is why the NHTSA would estimate the probability
> of driver/passenger injury to be twice as high in the 4Runner as compared
> to the Rav4 in a frontal collision. If anything, it should be the
> other way round. Could someone please help?

These are not seat-of-the-pants estimates; they are based on
instrumentation in the dummies themselves in an actual crash test. The
passenger-car-like RAV4 does a better job of absorbing the impact,
and/or of keeping its occupants in place, than the truck. That's not
that surprising: sheer masses of metal will never substitute for
careful engineering.

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.

[Steve Lewis]

One other factor to consider: these tests are performed by driving the
vehicle at a constant velocity into a stationary object. If the same
test were performed by driving both of these two vehicles at each other,
the test results would likely be different, simply because the lighter
vehicle would be absorbing a much larger percentage of the energy of the
impact. The important thing to remember about safety ratings is to
compare them against other vehicles in the same class. Generally
speaking, newer vehicles are safer than older vehicles, engineering is
very important, and size does matter in the real world. ;)

Steve Lewis