The Physics Behind Car Crashes

Guinnessy writes "Physics Today has an article on Vehicle Design and the Physics of Traffic Safety. The article analyzes in detail typical crashes experienced between cars, and cars with SUVs'. According to Marc Ross, Deena Patel, and Tom Wenzel, "The evidence is compelling that body-on-frame light trucks cannot safely coexist with passenger cars under existing conditions. That problem is critical because so many light trucks are used nowadays as car substitutes." They suggest some ways in which both cars and SUVs' can be redesigned to improve safety. Meanwhile Detriot News reports on a Pediatrics journal study says that claims that children are no safer in SUVs than cars because of the rollover risks."

Comments

I reckon..

[DeathByDuke]

..that one of their findings was that cars dont explode upon slightly touching each other!

Re:I reckon..

[Indy Media Watch]

That only happens to American cars which will always explode in a ball of flames, but not until the hero can pull the important passengers to safety, and yell, "Watch out! She's gonna blow!"

Re:I reckon..

[genner]

Yeah, it's gotten bad. Back in the 80's they realy knew how to make a car. Sure they would flip but everyone would get out unharmed , just in time for the A-Team to chase them down.

weight& speed are the big issue here

[jacquesm]

you don't have to be Einstein to remember that e=mv^2, and that if you want to reduce the damage to you, yours and the occupants of other vehicles you keep your speed down and your vehicle weight down.

Driving fast in an SUV loaded with kids is about as unresponsible as it gets, I see it quite often though...

Re:weight& speed are the big issue here

[i_should_be_working]

As others have pointed out, this has nothing to do with E=mc^2.

In addition, in a large vehicle the conservation of momentum is on your side. It's not the crash that kills you it's the sudden acceleration (your body going from 30 to 0 mph in a second). But if your vehicle doesn't change velocity much (because of its large mass, mass==resistance to acceleration) then you're fine. The other guy dies. That's why there don't have to be seat belts on buses (though it would still be a good idea). If a bus crashes into something, it's probably not going to stop very fast.

Large mass is not why TFA says SUV's are dangerous, it's because they tip over.

Re:weight& speed are the big issue here

[i_should_be_working]

Whoever is in the car that undergoes the largest acceleration is worse off. Since mass is by definition the resistance to acceleration, the ones in the larger car win. If two equal mass cars collide they both undergo the same acceleration. Ignoring car vs SUV strength, if two cars have a head-on collision at 30mph, the people inside are just as well off (or just as injured) as if it were two SUVs.

Re:weight& speed are the big issue here

[Vellmont]

And you don't have to be an Einstein to know that kinetic energy isn't what kills people, it's the sudden stop that does. If I jump out of an airplane and atain terminal velocity, but deploy a parashoot I'm a lot safer than jumping out of a tree. The point is that if all that extra weight is put into engineering stronger cars that absorb the impact and slow you down more gradually then you're going to be more likely to survive a crash.

That's not to say that SUVs are safer than normal cars. The rollover risks aren't trivial. Personally I think SUVs should be banned, or at least put into some special category of business only use because of the safety risks they put on other cars. The SUV craze is literally killing more people and making driving for everyone else less safe, and this article proves it.

Re:weight& speed are the big issue here

[owen_b2]

the same is true with antilock breaks

Since when? Are you alluding to the misconception that a good driver can stop faster without ABS than an average driver with? With modern ABS this just isnt true anymore, even if you're a rally driver.

And ABS systems let an average driver steer their car in a heavy-braking-potential-skid situation, where the non-abs car will be skidding in an uncontrolled straight line. How many drivers are taught cadence braking these days?

Re:weight& speed are the big issue here

[owen_b2]

This 1994 study is interesting http://www.nhtsa.dot.gov/cars/rules/regrev/evaluat e/808206.html

While it says that the most common accidents - rear enders - were decreased, it goes on to say "Rollovers and side impacts with fixed objects - crashes that typically follow a complete loss of directional control - had the highest increases with ABS. Nonfatal crashes increased by 28 percent, and fatal crashes by 40 percent. "

Re:weight& speed are the big issue here

[AndroidCat]

But strangely, the bus will rapidly gain mass after an accident, from all the people who said they were on the bus and want to file an injury claim. Even stranger, this mass gain happens even when the accident is simulated.

Re:weight& speed are the big issue here

[Alioth]

It is likely that this was not caused by the ABS itself, but an unintended consequence of ABS - people have a car with ABS, therefore feel safer, therefore drive faster or drive more recklessly because they think they can violate the laws of physics because they have ABS. I bet if a driver continues to drive carefully with an ABS equipped car they will be better off.

Re:weight& speed are the big issue here

[owen_b2]

Quite possibly.

But you can't ignore the fact that ABS lets you steer the vehicle in a 'panic braking' situation, and its this abilty to steer (cf skidding in a straight line) that lets people turn too hard and rollover their vehicle.

I'd have thought that the ESP systems that are becoming more commonplace would be able to reduce the problem though.

Having said all that, I still prefer my car with no driver aids.

Re:weight& speed are the big issue here

[saider]

From the
National Highway Traffic Safety Administration.

"Do cars with ABS stop more quickly than cars without?
ABS is designed to help the driver maintain control of the vehicle during emergency braking situations, not make the car stop more quickly. ABS may shorten stopping distances on wet or slippery roads and many systems will shorten stopping distances on dry roads. On very soft surfaces, such as loose gravel or unpacked snow, an ABS system may actually lengthen stopping distances. In wet or slippery conditions, you should still make sure you drive carefully, always keep a safe distance behind the vehicle in front of you, and maintain a speed consistent with the road conditions."

ABS is about control, not stopping distances. It allows you to retain control of your vehicle by preventing the wheels from locking up. As such, ABS will not reduce your velocity as much as tradtitional brakes and you will therefore impact with more energy.

However, the benefits of ABS and being able to avoid the collision outweighs the costs of reduced stopping force. So for the untrained driver who simply hits the brakes and waits for impact, ABS can result in higher impact velocities. but used correctly, ABS can help you avoid a collision altogether.

So in some cases (when you cannot maneuver) it is more dangerous, in some cases it is safer.

Re:weight& speed are the big issue here

[TigerPlish]

Lighter cars don't grip the road? How ignorant. Explain, then, the Mazda Miata, or just about any Lotus ever built? How about the old Porsche 914 and the little MGs and Triumphs? For that matter, how about a nice little crotch rocket with really sticky rubber? How come these sub-2500 pound vehicles can exceed the lateral G loadings of say a two-ton pickup?

The suspension design, its geometry, and MOST IMPORTANT, the tires determine grip. (for normal road cars. For all-out race cars, aero is another way to generate grip.. but aero grip goes away when you slow down.)

If you put 20 dollar Wal Mart tires on your car, you deserve to die horribly in a no-grip accident.

If you treasure your life, and that of those you love, then fer $DEITY's sake, put decent rubber on your car. And that' doesn't mean "all seasons". It means summer tires for when it's not snowing, and snow tires for when it is.

Mass is the enemy. Less mass makes for better driving cars. Better grip, better control, better handling. More mass, the American Way, just ruins everything. That's just one reason why EVERYONE builds better-driving cars than America does.

Of course, if you have a small weenie, then your psyche demands you get a big honking chunk of ill-handling, ill-stopping, ill-steering Detroit Heavy Metal. To compensate, y'know.

Re:weight& speed are the big issue here

[boingo82]

The point is that if all that extra weight is put into engineering stronger cars that absorb the impact and slow you down more gradually..

That's not necessarily what's being done.

Many of the largest SUVs (Suburban for example) are on a longer redesign schedule than your standard passenger vehicle. Going 8 years between a full redesign means you're still getting crash technology that's nearly a decade old.

Making matters even better, is that the largest of SUVs, by virtue of their GVWR (a number that's made up by the manufacturer) are not required to meet several bare-minimum government safety standards.
The current Suburban, with a GVWR of 7000-8600 lbs, is exempt from government roof crush tests. (PDF)(As is any vehicle with a GVWR over 6000 lbs.) Unfortunately, passing them wouldn't mean much either - as the minimum only requires a vehicle with windshield intact to withstand 1.5 times its weight pressed down on the roof.
In a rollover, the windshield is usually gone by the end of the crash, and forces can easily exceed 1.5 times vehicle weight.
The current standard has been in place - and unchanged - since 1971, and many SUVs aren't required to pass even that lax standard. Many are also exempt from other minimum standards, like Steering Wheel Rear Displacement (only applies to cars with GVWR 4,000 lbs and less), and basic braking standards (applies to vehicles with a GVWR of 7,716 lbs and less).

Detroit, of course, insists the existing rules are adequate - the rules that often don't apply to their vehicles.

Even better, it's been shown that they misrepresented data from their own tests to the NHTSA.

Obviously, we all have to be more proactive in researching the safety of the vehicles we purchase - and not just go out and buy something "big" that "feels safe". Often, we may be safer in that type of vehicle, but only in multi-vehicle-non-rollover crashes - and to what expense? Raising the weight of your vehicle may reduce the risk to your family by 1/3 in some wrecks, but you've increased it threefold to the other car.

Physics of car crashes aren't intuitive.

[danamania]

I'm reminded of an accident I almost saw several years ago. It was at an intersection where the east/west road had right of way, and the north/south road had a Stop sign. I was in a friend's shop at the time, and we heard a V8 accelerating hard, then a sudden very loud *thud*.

Running outside, we saw from the accident that a 1970s V8 Statesman with a P Plate (here, drivers get P plates to tack on their car for the first few years they're driving on their own) had obviously gone through the stop sign and hit the driver's side of a Prelude driven by an elderly driver. The young guy in the statesman was taken off to hospital, but a rescue team was needed to pull the driver out of the Prelude. Later that night the news had a piece about the accident, saying that the p-plater had caused an accident that killed the elderly guy. Even witnesses at the scene said they heard the V8 go through the intersection far too fast, and hit the prelude.

Then the next night, video shot from inside a building nearby showed the accident - the P-plater had actually stopped at a pedestrian crossing, let the people walk across, then accelerated quickly & noisily... but he was actually moving along the east/west road with right of way. It was the driver in the prelude that had gone through the stop sign at high speed, and the young fellow was just in the wrong place at the wrong time, and hit the driver's side of the prelude hard - both cars went spinning around in an impossible looking way, ending up in a position that looked for all the world like the young fellow had gone through the stop sign, even though in this case the only thing he'd done 'wrong' was make a big ol' noise in first gear. My "obvious" guess at who was in the wrong was completely off.

There's a massive amount of energy in a car collision, more than most people would expect given how much we take moving a tonne or two of steel from one place to another daily.

Re:Physics of car crashes aren't intuitive.

[Gordonjcp]

I've seen pictures of a crash involving a Renault Megane, and a Hummer H2. The H2 ran through a red light and got cokebottled by the Megane. So - SUV versus small European MPV. Sounds like no contest, right?

Damn Straight.

The Megane was very severely damaged, with the driver and front passenger sustaining some injuries, mainly limited to cuts from glass and severe bruising. The passenger hit her head on a bent bit of A-pillar.

The H2 was *destroyed*. The impact knocked it on its side, and pushed the gearbox and transfer box through the floor and out through the roof. The chassis was split in two from about the middle up to the front crossmember.
I suppose I don't need to draw any pictures of what this did to the four occupants.

Re:Physics of car crashes aren't intuitive.

[Kadin2048]

I find that hard to believe, but even if it's true, it's hardly representative of most SUV vs. passenger car crashes. It's just not. Perhaps the H2 is just poorly constructed in terms of side-impact protection or something, I can't say since I'm not familiar with it, but imagine that same collision occurring head-on. It barely matters what equipment each car has, because the H2, having much more mass, is going to decelerate much less violently. It's just not going to experience as serious a collision as the smaller car will.

There are many studies which support this (besides TFA), and I've personally seen (as an EMT) some really hideous SUV/Car collisions, and can tell you: the SUV usually wins. Sometimes there are mitigating factors, like the SUV will roll over and throw out and crush anyone that's not seat-belted, while the car will basically stay in one place, but if you have the choice between being in a Honda Civic and a GMC Suburban with similar safety equipment when they run into each other, you'd be insane not to pick the Suburban. Plus, the increased size of the car makes it likely that you'll get extricated from the vehicle a lot faster (again, assuming no rollover).

The biggest problem with SUVs, traditionally and still, is that they tend to roll over during hard panic maneuvers, or when hit from the side. Where I used to live, the biggest risk was people driving them too fast for conditions (no, your SUV does not mean you can drive on ice) and laying them over -- generally nonfatal though. But in a straightforward front-end or rear-end collision, there's something to be said for surrounding yourself with several thousand extra pounds of steel. Granted, you get that advantage at the expense of the person in the smaller car, and you have to be more careful taking it around a corner, but it's there nonetheless.

Re:Physics of car crashes aren't intuitive.

[the_bard17]

The biggest problem with SUVs, traditionally and still, is that they tend to roll over

Not from my point of view... their problem is this: the SUV usually wins. From my meager time in life, I've seen plenty of reckless drivers. Not all of them were teenagers... I've seen my share of reckless soccer moms, businessmen, and delivery drivers. Quite a few of these drive heavier vehicles. I suppose it makes them feel safer, being in a heavier vehicle (which they probably are).

They continue their reckless driving habits, however, now becoming that much more of a threat to the general populace driving smaller cars. They may be more likely to survive, but they're decreasing the chance of survival for everybody else.

Until everybody "wises up", goes out and buys an heavier vehicle... at which point we're right back at square one, with worse gas mileage.

Re:Physics of car crashes aren't intuitive.

[arivanov]

Meganne safety rating is off the scale. The occupant safety level is so good that they are having to redesign the tests because of it. At 35 mph collision of any type (front, side flat, back and side pillar) there is no damage to the occupants. At all. The test result is all green with a possible minor spot of yellow (which corresponds to a bruise). Just look at the EUROncap safety tests http://www.euroncap.com/. Same for every Renault made in the last 3 years.

At the same time the Hummer is not even on the list. In fact if it was, it would have pulled a 2-2.5 star rating at best. Same as a suicidal box like Fiat Ceicento. I have seen a crashed Hummer so this unscientific opinion is based on seeing what happens when it smashes. If you are driving this POS you have a death wish.

Essentially even being in a something microscopic by American standards (like Modus http://www.euroncap.com/content/safety_ratings/det ails.php?id1=1&id2=201) is safer then being in a Hummer.

Re:Physics of car crashes aren't intuitive.

[Zog The Undeniable]

The insurance companies aren't screwing you (or at least, no more than anyone else). They use actuarial tables which show the average younger driver, or any driver with no clean driving history, is several times more likely to have an accident.

Now I was never a particularly aggressive driver (and the only accident I ever caused was when I reversed into a concrete pillar) but I can safely say that in 19 years of driving I leave a lot more space in front and anticipate other drivers' bad behaviour better than I used to. Hell, when I was 25 in a little 988cc car I used to drive a section of country lane in about half the time that I would risk it now - in a car with 2.5x the power. It's all about testosterone and perceived invincibility.

Re:Physics of car crashes aren't intuitive.

[skaffen42]

Too true... unfortunately it seems that SUV drivers believe the hype that they are invincible. I'm "trail-rated" so I can go anywhere at any speed!

I saw the result of this last Saturday when there was some freezing rain early in the morning. Driving down Route 80 I counted 14 accidents in the space of about 20 miles. The majority of the vehicles involved were SUVs, and when a car was involved it was usually because an idiot in an SUV had rear-ended them. Worst accident was some large SUV that looked liked it had rolled end-over-end. Couldn't have been more squashed if it had been hit by a train.

The combination of vehicle weight and perceived driver invincibility seems to make SUVs deathtraps in anything other than perfect driving conditions. Ironic, when you think about it.

Re:Physics of car crashes aren't intuitive.

[killjoe]

"Quite a few of these drive heavier vehicles. I suppose it makes them feel safer, being in a heavier vehicle (which they probably are)."

They probably are safer in their huge SUV. Too bad they are not thinking about the people they will murder though. If they were driving a lighter car which would more effectively crumple and absorb impact the people in the other could maybe survive.

I guess it re-inforces the stereotype of the SUV driver as the guy who doesn't give a shit about anybody else except themselves. Don't care about the environment, don't care about foreign oil dependency, don't care about the survival of the other guys in the crash.

Re:Physics of car crashes aren't intuitive.

[Karma Farmer]

I suppose I don't need to draw any pictures of what this did to the four occupants.

This is how we know you're lying -- no H2 has ever had four passengers at the same time.

Unless you mean the driver and three bags of groceries.

European car security

[sucker_muts]

The newest european cars nowadays come with an extra protection agains collisions with pedestrians: The hood in front of the car is lifted a few inches after 40 or so milliseconds so the pedestrian gets lifted as well and won't get run over by the car but lands on the softer hood and might hit the car glass.

The powertrain generally takes up considerable space in the engine compartment, leaving little room between the engine and the bonnet.
To remedy this, the C6 comes with an active bonnet system as standard that automatically raises the bonnet in the event of pedestrian impact. Thanks to an impact sensor and pyrotechnic mechanism, the bonnet rises 65 mm in 40 milliseconds. A second mechanism maintains the bonnet in its raised position despite the impact and thus absorbs the deformation energy.

Example from Citroen.

Re:European car security

[smchris]

Me too (usually a pedestrian). There are significantly more pedestrian deaths in the U.S. _every_year_ than the World Trade Center deaths but I don't see people getting all weepy over it. (http://www.carwrecks.com/info8.html)

Being a long-term survivor of pedestrianism is one of the best ways to become a cynic of the human condition. It annoys me that my local media have to make a point that "alcohol and drugs were not involved" -- to which I always think, "Great, a clean kill." Running over a pedestrian is the safest way to experience the thrill of murder. Unlikely you'll even get the workhouse if you aren't too blatent about it. But be warned that if you only wing your pedestrian you could be paying off the multi-million dollar lawsuit for the rest of your life under the new bankrupcy rules. So in the end it's smarter not to run over pedestrians, ok?

[Aside from personal experience, I tend to be even more cynical because working in various places and talking about walking to work I have met _three_ secretaries who each had their father killed at a stop sign or stop light pedestrian walk.]

Well, that settles it then...

[shmlco]

"The evidence is compelling that body-on-frame light trucks cannot safely coexist with passenger cars..."

Well, that settles it then. It's obvious we need to outlaw passenger cars. Not only will that remove millions of unsafe cars from the road, it will give a much needed economic boost to the SUV manufacturers.

Besides, if a car is unsafe around a light body truck, it must be a death trap around a standard truck or a semi-tractor trailer rig...

Re:Well, that settles it then...

[Oldsmobile]

"I find it amusing when the vehicle is blamed rather than the operator.

I agree. Seatbelts ought to be BANNED and a large spike pointing at the drivers chest should be fitted on the steering column. Not only would it make people drive really safely, it would cut down on motoring.

Re:get some priorities!

[radja]

ok then. let's have a party.

Canyonero!

[Life700MB]

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65 tons of American Pride!

Canyonero! Canyonero!

Top of the line in utility sports,
Unexplained fires are a matter for the courts!

Canyonero! Canyonero! (Yah!)

(Entire lyrics here)


--
Superb hosting 20GB Storage, 1_TB_ bandwidth, ssh, $7.95

You're both wrong. or right.

[tabrisnet]

KE = (m/2)*v^2

or the more common form: KE = 1/2mv^2

This incidentally does make it in the same class as E=m*c^2 (due to magnitude/exponentiation) but that's more or less irrelevant.

Chinese SUV

[lovebyte]

I don't know for the USA, but a chinese SUV is being imported into Europe and it received a 0 rating for safety.
So be careful! If you see one on the road, stay well clear.

Re:Chinese SUV

[bobdotorg]

Overheard at a cafe in Stockholm:

Volvo Engineer: But your SUV is so dangerous - it has no crumple zones.

Chinese Car Salesman: Silly Swede. You Volvo my crumple zone.

Re:Chinese SUV

[10Ghz]

Actually, looking at the videos and pictures of the Landwind crash-test, it becomes quite obvious that the whole car is one big crumple-zone. The car seems to simply disintegrate.

See for yourself

People will always buy an auto they feel safe in

[fantomas]

People are always going to consider their own selfish personal safety as a purchasing factor when choosing a road vehicle; for many people this is a very significant issue, and is played upon by advertising for autos.

We need to focus on methods of ensuring safety that don't threaten other road users: win-win situations rather than soccer moms driving trucks and declaring "I know I will win in a collision" (vaguely remembered quote from a National Geographic article on SUVs). This can only lead to a sort of arms war where we all end up driving 38 tonne truck rigs....I was particularly scared by the picture of the SUV built on what is effectively a couple of forward facing railroad rails - that's going to hurt if you're hit side on in a little compact by one of those.

The annoying thing is I am sure most of the safety issues can be solved with little cost and by improving social as well as technological aspects of road use, e.g. severely enforcing low speed limits round residential areas. As long as its cool to drive like a bastard people will.

I always like the story about how there were a lot of fatal accidents in early autos because of the bolt protruding in the middle of early steering wheels, head on crashes meant drivers suffering lots of chest damage; while this was then changed to make life safer, it's been pointed out that if there was a big spike compulsorily welded onto the middle of all steering wheels pointing at drivers then everybody would drive a whole lot more carefully and there would be a lot less accidents.....

This Is Genius!

[ObsessiveMathsFreak]

The hood in front of the car is lifted a few inches after 40 or so milliseconds so the pedestrian gets lifted as well and won't get run over by the car but lands on the softer hood and might hit the car glass.

Wow! That's great! Now instead of plebs getting messily caught in my undercarraige, they'll just hit the bonnet and windshield and bounce right off! I can just turn on the sprinklers and wash the blood right off while I sip on my latte! This is genius!

The only downside I can think of is that they may be inconsiderately be wearing metallic objects that might scratch my paintjob. That's a serious issue with this system. Perhaps it would be better if they were bumped to the side instead, preferably to the sidewalk, as that way they wouldn't fly into any oncoming drivers, thus exacerabting the problem.

On SUV safety

[Oldsmobile]

Funny thing anout SUV's. They really are a hazard. Not only is the center of gravity higher, but they usually have misdesigned suspension (Ford Exploder, Mitsubishi Montero) that actually encourages rolling over, SUV's have higher bumpers, so cars running into them slide under, killing the occupants in the lower car. SUV's use more gas and cause more pollution. A very big problem is roof crush. SUV roofs are notorious for being frail and crushing in a roll over accident, squishing the people inside.

I for one don't like the idea of dying by having my spinal column driven into my skull.

Many of these things of course could be mitigated. There could be a standard lane change test to determine suspension quality, there could be rules on the center of gravity, there could be rules on bumper height (like on regular cars) and there could be rules on pollution, perheps making all SUV's except the kind with frugal modern common rail diesel engines (with particle filters) financially impposible to own/buy.

But this is not the case. Infact, with GM and to some extent Ford in financial trouble (and with all their profits coming from SUV's) the current US administration wil do nothing about the laws, that infact make SUV's above the law.

Right now, SUV's are excempt from current fuel efficiency laws (that are not very good in the first place, mind you), they are excempt from bumper laws (making SUV's lousy and expensive to fix in even the smallest parking lot accident) and there are no laws governing roll-overs (only tests).

With all these problems, I don't see why they even allow these on the road.

The funny thing is, I really like the idea of sitting up high in my car and being able to see further. That is probably the only reason SUV's are so popular. Looks like they could accomplish that in a macho looking vehicle without these problems.

Cross-over anyone?

Re:On SUV safety

[RosenSama]

Many of these things of course could be mitigated. There could be a standard lane change test to determine suspension quality, there could be rules on the center of gravity, there could be rules on bumper height (like on regular cars) and there could be rules on pollution, perheps making all SUV's except the kind with frugal modern common rail diesel engines (with particle filters) financially impposible to own/buy.

The car buying market in the US is pretty democratic. People buy what they want. We don't need more rules here to tell people what they "should" buy any more than we need more rules about televisions telling people what they "should" watch. The reason the SUV-is-a-truck-not-a-car loophole that excludes them from bumper height and fuel economy exists in the first place is because of short-sighted rules. We don't need further rules that just leave new loopholes with age. Eventually the car manufacturing regulations would be like the tax code.

Re:Wimpifying the SUV's and Trucks is not the answ

[Vellmont]

And when the drunk moron is driving an SUV and hits you in the side, you and your family will be dead. Had he not had all the "armor" you and your family might have lived

what is the definition of "safely" ?

[tjic]

"The evidence is compelling that body-on-frame light trucks cannot safely coexist with passenger cars "

The author of the study is making the mistake that safety is a boolean, and that things are either safe or unsafe.

In fact, everything is unsafe, to varying degrees. ("Life", in the words of Warren Zevon, "is gonna killa you").

The important thing, when contemplating questions of public policy, is to COMPARE one risk to the next, and make sure that we're making reasonable decisions and tradeoffs.

For example, over the last 10-15 years, a lot of states have dropped the DUI (driving under the influnce) BAC cutoff (blood alcohol content) from 0.1% to 0.08%. Lower is better, right?

Well, as it turns out, having a BAC in the 0.08 - 0.10% range has the same effect on driving ability as (a) having a cold; (b) getting a poor night's sleep; (c) being over the age of 50.

If we're going to make a 0.81% BAC illegal (and punish it with major fines), should we not also have the same punishments for driving while having the sniffles, or while being 51?

The answer is that one behavior gets a penalty because it sounds good, makes politicians look like They're Doing Something(tm) and has moralistic overtones ("get those damn drunks off the road!").

To say that "light trucks cannot safely coexist with passenger cars " is purest nonsense. We've had light trucks coexisting with passenger cars for 70 years, and the fatality rate drops every single year. Sure, if you could snap your fingers and get every pickup truck, minivan, delivery van, and SUV off the road, things would get incrementally safer for the average driver of a passenger car. ...but how much safer?

I don't know off the top of my head, but is it a level of safety comparable to every passenger car driver making sure that their tires are fully inflated before each trip? Or more, or less?

Absolutist boolean statements like "X can not safety coexist with Y" do not answer questions like this. These statements are public-policy-by-press-release and deserve to be condemned.

Re:People will always buy an auto they feel safe i

[dkleinsc]

The SUV craze is actually the same phenomenon as the crowded theater phenomenon (where someone stands up to get a better view, so soon everyone is standing to see at all, and no one sees any better than when they were sitting). The idea is "If my vehicle is heavier than the other guy's, then in an accident I'll be in better shape than him." End result: Everyone will go out and get a bigger vehicle, because it appears that will make them better off, and as a result no one is safer.

Of course, the heavier vehicles always create a false sense of security. Trucks and large vehicles are more prone to rollovers, can't stop or swerve easily to avoid trouble, and hit stationary objects with more momentum. But like Homeland Security or MS Windows, it makes you feel safe, so people choose to go with it even if the facts are completely against them.

Really your best defense while driving is to actually use everything you learned in Driver's Ed, or if you don't remember than find books or classes on safe driving. And if there are any teenagers reading this, remember that Driver's Ed is the one class most likely to determine at some point whether you survive a situation. You know, driving at reasonable speeds (somewhere around the speed limit is usually good), slowing down before you take corners, being aware of the drivers around you, good signalling so other drivers are aware of you, etc.

Mini vans vs SUV's

[pease1]

I've always been struck (pun intended) how the day I grew up and traded my SUV in for a mini-van that is about the same weight and gets about the same miles per gallon, I suddenly became more policitically correct, safer and less of a risk to everyone one else on the road.

And they say there is no free lunch.

Funny thing is, other then the "coolness factor," I do everything I used to do in the SUV with the van, and the van is actually better at it since it carries more. This likely includes more off road travel then most SUV's ever see.

Obligatory Simpsons quote

[ning]

Can you name the truck with four wheel drive,
smells like a steak and seats thirty-five..

Canyonero! Canyonero!

Well, it goes real slow with the hammer down,
It's the country-fried truck endorsed by a clown!

Canyonero! (Yah!) Canyonero!
[Krusty:] Hey Hey

The Federal Highway comission has ruled the
Canyonero unsafe for highway or city driving.

Canyonero!

12 yards long, 2 lanes wide,
65 tons of American Pride!

Canyonero! Canyonero!

Top of the line in utility sports,
Unexplained fires are a matter for the courts!

Canyonero! Canyonero! (Yah!)

She blinds everybody with her super high beams,
She's a squirrel crushing, deer smacking, driving machine!

Canyonero!-oh woah, Canyonero!

Support your local lyrics site!

Crash Ratings don't say what you think

[CFD339]

As a firefighter and first responder I can state that there's a big problem with the safety crash test ratings most consumers see. These 4 star and 5 star ratings don't tell the real story at all.

These tests emphasise not just the human safety but also the cost of repair. To some extent, the cost of human repair is the factor added to the vehicle repair to make the rating. Interesting data, but not what most of us care about, and it results in very poor decision making information.

Example: I have seen personally how effective "crumple zones" combined with airbags and safety brackets on hoods which prevent the hood from sliding directly back into the windshield in the case of a head on collision can work. I see completely destroyed cars all the time where the occupants are well protected and suffer only minor injuries. That's because much of the force of impact is used up in the act of crumpling the car. These crumple zones are amazingly effective.

The problem for insurrance companies is that crumple zones and the like TRADE vehicle damage for human damage. The low-speed destruction of bumpers, fenders, hoods, and entire engine compartments mean that these cars are a "total loss" much more frequently.

If you REALLY want to promote SAFETY -- and like me, you could care less about the damage to the vehicle if the humans are better protected -- than we need a safety rating system which ignores all things other than damage to the occupants of the vehicles.

AP

Size is important.

[MaWeiTao]

I personally hate SUVs. I think the fundamental problem in the United States is that drivers licenses are given out too easily and the base license gives a driver access to too many different kinds of vehicles. SUVs should require special licenses with extensive driver education.

The problem comes down to driver ignorance and stupidity. This, however, isn't something unique to SUV drivers. Around where I live there have been countless idiots crashing into various objects in their beat-up, riced-up small Japanese imports. The city can't do anything to beautify the city without one of these morons coming along and destroying it. They sure do a good job of flipping those cars over too.

That said, mass is a huge factor in determining passenger safety. Of course there are situations where people in a smaller car fare better than in the larger car, but that's the exception.

We have all these crash tests which award the same high marks to a small car that they do to a large car. But these tests are performed under controlled conditions in the kinds of impacts people rarely encounter in real life. These tests are also conducted at relatively low speeds. The kinds of speeds drivers on the road are exposed will completely destroy a car regardless of all the safety features car makers install. And a driver in a large car has one simple advantage: there is more of the car to crash before the impact reaches the driver. I've heard from a few sources that a driver in a small car is up to 13 times more likely to die in a small car compared to a large one.

Of course, if you're driving something as poorly built as that Jiangling nothing will help you, but that's another story. I'm surprised that Europe, with all it's regulations even allows the thing to be sold there. Then again, considering some of the things I've seen on the road there, it's not too surprising. The US is fairly strict. The ride height for the new Golf GTI was raised .5 inches to meet US bumper height regulations. And there are countless other vehicles not allowed here because of things like lacking 5mph bumpers. I guess the US government needs to make up for the fact that Americans are generally poor, irresponsible drivers.

Unfortuneately...

[bmajik]

the best way to be a safe driver is situational awareness.

You can choose to optimize for avoiding accidents, or you can choose to optimize for an irrational hope that the ones you do have will be survivable.

By selecting an SUV, you've done the latter.

However, by doing so, you've chosen to have more accidents, more often. SUV's, irrespective of any other factors, have less grip than lighter vehicles merely because of their excessive weight, and because the load/grip ratio on modern tires is non-linear.. there's a fall off as load increases.

Additionally, the excessive girth of most SUVs means that you're fighting significantly more inertia than other vehicles. The horrible twist and non-rigidity in the construction means that any evasive maneuvers are uselessly slow - the body of the truck twists instead of directing the tires to move.

Everything the vehicle does is slow.. numb... subdued.

The high roll center means that more weight is transferred in all accelerative movements.. when turning you move more weight to the outside edge.. when braking you unload the rear tires more.. prior to high-roll-center SUVs being commonplace, rollovers were pretty much unheard of on paved roads. (when you leave the road, that's a different story).

even if you are the most situationally aware driver, when you pilot an SUV, you are motivating a stick of butter across a pan. You're driving a numb, useless instrument instead of a precision machine with proper dynamics.

You will be in more accidents, because you're driving a vehicle more likely to roll, more likely to twist/bend under dynamic conditions, that takes longer to stop, turn, and change direction, and which has lower road-adhesion characteristics for a given tire design than a lighter car would.

Also, your increased mass will tend to cause more damage to others around you.

All of this.. because you think you are better off if someone hits _you_? You've chosen a vehicle that makes it more likely you'll get hit (because it cant evade effectively.. and it's an enormous target). Your vehicle is more likely to roll in a side impact. Your vehicle has a very weak chassis, so unless the collision hits in just the right spot, the amount of body deflection and passenger intrusion will be more severe than in a well made unibody car.

I live in the midwest, so i understand the utility and necessity of large, ladder-frame vehicles perfectly well. But i dont own one, because i am not a farmer, construction foreman, or other blue-collar contractor. Trucks and SUVs have a purpose, but passenger safety for daily driving isn't it.

Congratulations, you've been deluded.