Huge study about safety can be misinterpreted by SUV drivers

Recently (October 14, 2003) the National Highway Traffic Safety
Administration (NHTSA) released a study about vehicle safety and
weight. See:

http://www.nhtsa.dot.gov/cars/rules/regrev/evaluate/pdf/809662.pdf

As expected, the NHTSA study did find that heavier vehicles are safer
for their occupants when they crash with a lighter vehicle. This is
well known, and many people buy SUVs thinking that their weight gives
them a safety advantage. Some publications stress this fact (for
example one by USA Today is titled "Lighter cars mean more deaths" so
many people who drive SUVs may feel reassured).

In fact, as far as SUVs go, the NHTSA study could not have been more
unfavorable. Using real world statistics about tens of millions of
vehicles over several years they prove that the overall safety of SUVs
is worse than of lighter passenger cars. One of the reasons is that
SUVs have a much higher tendency to roll over. This means that many
people spend more to buy a SUV, spend more on gas, and also endanger
others, without much any advantage for themselves. The relevant
numbers are:

Vehicle type Average weight Driver fatalities
(pounds) per billion miles

Mid-size 4-door car 3,061 5.26
Large 4-door cars 3,596 3.30
Small 4-door SUVs 3,147 5.68
Mid-size 4-door SUVs 4,022 6.73
Large 4-door SUVs 5,141 3.79

So it is more probable that you will be killed in a small or mid-size
SUV than in a mid-size car that weights less. Only large SUVs are
safer for their drivers than mid-size cars, but they are less safe
than large cars, even though large SUVs are 1,500 pounds heavier!

These are amazing numbers. The prorated figures, which take into
account the fatalities in other vehicles involved, are, as expected,
even worse.

The study does show that SUVs are safer than small and very small
cars, which have a disadvantage only because there are so many much
heavier vehicles around. Very few people who end up buying a SUV were
thinking of maybe buying a small or very small car, so this advantage
is irrelevant. Pound for pound SUVs are always less safe for their
passengers.

Even when comparing SUVs only, more weight is not always better.
Significantly, small SUVs are safer for their drivers than mid-size
SUVs, even though the latter weight 900 pounds more. I suppose small
SUVs are more car-like and therefore avoid some of the safety
disadvantages of the SUV design.

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.

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. Vehicles that have to be heavy
(such as trucks, heavy duty off-roaders, buses, etc) should have their
top speed electronically limited to low levels as to not endanger
other vehicles on the asphalt.

 

These numbers are in no way amazing. Large passenger cars have come
out on top in every study I've seen of this type. However, it is these
safest vehicles are discouraged by regulations on the books. (CAFE)

Is this with or without a repeal of CAFE? Passenger car weight is
effectively capped with CAFE. Also where would that cap be? 2000lbs?
4000lbs? 6000lbs? Given political implementations your weight cap
could easily result in making things worse.

 

I care not only about my safety, but the safety of my family, so I
bought a very safe SUV.

Go figure.

 

Studies cannot prove or disprove. There are so many variables in data
sampling and collection and analysis and interpretation that all they can
do is suggest. They can strongly suggest, but they cannot prove. Any
reputable and ethical scientist will tell you this -- it's only the
political latchers-on who run around claiming to have a study "proving"
their agenda is correct. Nevertheless, let's move on to your further
"analysis":

Fortunately, your odds of being killed as the driver of ANY of the listed
type of vehicle are reassuringly tiny. 6 deaths per billion VMT is indeed
double 3 deaths per billion VMT, but so is two molecules double 1
molecule. It's important to keep numbers like this in context: You're
extremely, extremely unlikely to be killed as the driver of any of the
above vehicles.

Only to the ignorant and to the politically opportunistic. They're not
amazing at all. They're perfectly predictable and logical numbers.

The study *suggests* that SUVs are safer than small and very small cars.

Nope. The study doesn't reach that conclusion. This sounds like
editorializing on your part. It most certainly isn't supportable by fact.
Small cars collide with all kinds of more massive objects, not all of
which are larger vehicles.

This sounds like more editorializing on your part. No factual support is
offered for it.

Whoops, no. We were were discussing *driver* deaths by vehicle type per
billion VMT. In fact, small cars are less safe for their *passengers*.

Y'know, Dianelos, I'm getting the sneaking suspicion you are ignorant,
politically opportunistic, or both. I think you have an agenda and are not
simply reporting facts as you claim.

....cannot be determined by death rates measured on the order of single
digits per billion vehicle miles travelled. There are much larger, more
pervasive everyday threats to real-world personal safety than whether
you're the driver of a large car or a large SUV.

This is your uninformed opinion, unsupportable by facts.

This is your uninformed guess, unsupportable by facts.

Pure conjecture, unsupportable by facts.

Wishful speculation, unsupportable by facts.

CAFE has effectively limited the weight of passenger vehicles. CAFE has
been shown to cost lives for exactly this reason. When you're done
learning about the basic principles of science and statistics, you need to
go study the law of unintended consequences, and when you're done doing
that, spend some time thinking up a way to limit the "weight" (you mean
mass) of bridge abutments, old oak trees, freight trucks, power pylons,
long-haul buses, moose, deer, and other things people hit while driving.

There is no support for the notion this would improve safety at all.

DS

 

.... yawn ...

- Jeff G
67 Kaiser Jeepster Commando
50 Willys 4x4 Station Wagon
http://jeffgross.com/willys

 

This is just ridiculous... comparing apples & oranges isn't helpful.

The advantage in a large vehicle is in vehicle to vehicle collisions; there
is no advantage in single-vehicle accidents (i.e., rollovers). The large
vehicle ALWAYS enjoys the advantage in any collision with a smaller vehicle.
Attempts to deny that simple fact based on the laws of Physics using all
kinds of clever statistical manipulations are simply absurd. Different
vehicles enjoy advantages in different types of accidents based on their
characteristics; wide-brush prejudicial generalizations don't help rational
folk in the task of making informed decisions. This, and messages like it,
are just political propaganda... plain & simple.

Rollover:
advantage: low center of gravity
REASON: increases leverage required to roll (lever angle)
winner: lower - heavier makes it better
loser: higher - lighter makes it worse
advantage: wide wheelbase
REASON: increases leverage required to roll (lever length)
winner: lower - heavier makes it better
loser: narrow - lighter makes it worse

Collision:
advantage: high MASS
REASON: more mass reduces accelerational forces after collision
winner: heavier - good crash test performance makes it better
loser: lighter - poor crash test performance makes it worse

Spinout:
advantage: long wheelbase
REASON: increases leverage required to spin
winner: long - heavier makes it better
loser: short - lighter makes it worse

Mixing the statistics for these VERY different types of accidents is poor
statistics at best... and deceitful or even outright dishonest at worst.
But these are the political times we live in...

The comment about limiting size for everyone is socialist at best, communist
at worst... and very authoritarian for sure! There's no reason that large
vehicles can't be A LOT more economical... why not concentrate on that?

The comment about limiting speeds for trucks, etc., is just absurd. Can you
imagine the outcry from the truckers? We can't even get them to obey the
speed limits now! Not to mention that while the standards for my vehicle's
exhaust have become draconian, nothing at all has been done about truck and
bus exhaust. Nor are there any CAFE standards for their fuel efficiency.
If this was a real effort to increase safety & ecological concerns then
TRUCKS & BUSES are the place to start!

And, just to top it all off, do you really think you're safer hitting a
large truck with your tiny car just because you made the truck drive slower?
If so, THEN YOU DON'T UNDERSTAND THE PHYSICS AT ALL!

And this is just the beginning... counting casualties in OTHER vehicles is
just GOOFY... penalizing your choice because the other guy failed to make a
similarly good choice is RIDICULOUS!

Politically motivated propaganda isn't just bad science, it's USELESS as
well.

Bob

 

You are an idiot bud.

If everyone drove heavier vehicles, fatalities would go down just as the
numbers below indicate.

I do note you don't show any numbers for little econo boxes. Why, are
they something like 10 fatalities?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

 

Approximately 10/17/03 08:52, Dianelos Georgoudis uttered for posterity:

NHTSA. Your government agency working against Darwin to keep
alive yet more fools who can't be bothered to buckle up, check
the air in their tires, or tell the difference between a
Ford Explorer and a Porsche in cornering capability. Great work
guys.

 

Not so.
I can control my own vehicle, especially in single-vehicle type
crashes.
I *can't* control other drivers who hit me.
My own record shows that the latter is *FAR* more likely to happen
(and overall statistics show the same), so I am, in fact, safer in my
large SUV.

Only relevant for some fictional person who is a conglomerant of all
drivers. Such a person doesn't exist.

Not so!
Trying to apply such numbers to individual drivers is false; they
apply to a *class* of drivers, not to individuals.

The figures above are for drivers; they do not apply (nor do they
purport to apply) to passengers.

Again, you are trying to apply figures that apply to a *class* to
individuals.
Do you conform to figures that apply to any large class of people? I
doubt it.

Really? Driver ability has nothing to do with it?
Or needs?

Vehicle weight is already limited by CAFE.
Lowering the speeds of heavier vehicles like trucks is more dangerous,
since that would increase the speed differential of colliding
vehicles, worsening the effects all around. Not a good idea. It's been
considered countless times, and rejected.

 

"Dianelos Georgoudis" <> sez:

Get thee astride a motorcycle and do even so much more ...

Good ridin' to ya,
VLJ

 

Heaver is better. Take a large SUV, spend a few bucks and put in a roll
cage, fire bottle system, and 5 point belts and you will be as close to
bullet proof as you can get.

 

Obviously, then you *expect* to wreck, as you've apparently traded
handling for crash safety.

What are you doing reading rec.autos.DRIVING then?

I got no problem with SUVs, as long as they are used for their intended
purpose(s) - i.e. hauling stuff, towing, off-roading. But for commuting
or store running, it's just freaking retarded.

nate

 

These stats alone tell you next to nothing. It is also well know that
drivers are involved in accidents in substantially different rates based
on age. If the large cars are being driven by people in the safer age
ranges (very likely) and the SUVs are being driven by people in less
safe age ranges (a good chance), then death rates (which are typically a
function of accident rates), will be higher for the vehicles driven by
the class of driver that has higher accident rates.


Matt

 

Really? I expect that a collision between two SUVs would be more
dangerous to the vehicles' occupants than a collision between, say, two
VW Golfs (Golves?) due to the construction of the various vehicles.

nate

 

The same could be said of practically any motor vehicle, even a geo
metro.

 

Why do you think that? The SUVs have a lot more distance between the
drivers and the front of the vehicle meaning that there is more distance
over which to decelerate and this means the deceleration forces could be
drastically less.


Matt

 

Probably not, as most cars are now unibody and a "real" SUV has a beefy
full frame. So the car will "crumple" better, unless it's a really
beefy (i.e. very high speed) smack.

nate

 

Nah, despite your wish that things were that simplistic, it's not the
case.

My SUV is quite safe and handles quite well.

Oh, part of it is the amusement derived from reading funny posts like
yours I suppose.

Fortunately Nate doesn't make up the rules.

What a great country, eh?

 

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.

This latest report follows the same trends for what must be a couple
decades by now.

 

Not necessarily. The frames are designed to crumple as well. Probably
the best available indication would be their respective performance in
crash tests. These are imperfect to be sure, but they are about the
best we have at present.


Matt