Actually the headline on the New York Times story says Study Says Minicar Buyers Sacrifice Safety. But the study looked at head-on collisions between minicars and larger cars (twice as heavy in the case of Smart vs Mercedes C class). Since momentum is conserved, a car weighing half as much experiences twice the change in velocity in a head-on crash and hence is much more dangerous to the occupants in such a collision.
But whether a minicar is safer or not depends on your perspective. It's more dangerous for the occupants, but it's safer for the people in the bigger car. The NYT article ignores this fact. Furthermore, because of a effect known as risk compensation, drivers of minicars will be more cautious because they are more at risk in a collision, thus making them even safer for other drivers than the physics of collisions suggests.
Of course, this benefit goes to other road users, so this suggests that there should be a tax break for minicars to encourage people to use them instead of bigger, more dangerous cars.
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I don't think they ignored that fact, Tim, I just think they are ignorant. They've been demonstrating this fact for a very long time on a range of subjects.
Your version of the story is very similar to the story of delivery drivers in a certain country, the name of which escapes me. The company was having a difficult time because their drivers were involved in many accidents. They started a new policy of "we don't care who's fault it is, if you are involved in an accident you lose your job, end of story." They then paid the drivers twice the going rate for delivery drivers. Accidents for all intents and purposes ceased. Don't know for certain if the story is true, heard it back before the internet, and can't find it on the internet.
Anyway, I've often thought about making cars lighter, but yes that puts the occupants at a disadvantage should they be involved in a collision with a conventional vehicle. However, this should be overcome one day with the advent and use of driver assist technologies that will help us avoid accidents due to lack of attention etc.
I don't know. The guys at Top Gear smacked a remote controlled Smart car into a 20 ton barrier at 70MPH. There was barely any deformation of the passenger cabin.
However they did mention that while the car itself wouldn't crush you, the massive deceleration would. Almost forgot to mention, the car MOVED the 20 ton barrier.
Experience argues against your theory.
The injury rates for smaller cars have been higher for decades. If it REALLY made drivers more cautious, to a degree that it reduced injuries, we would see that.
Interestingly, my wife just bought a used Mercedes and before we committed, we looked up what it would do to our insurance bill... which the insurance company broke into component parts. The experience-based medical coverage cost was 40% below average.
On the extreme end your theory would suggest that motorcyclists would be an extremely cautious group.
The story did quote the insurance policy group's recommendations, though at the very end. One recommendation was to make conventional vehicles lighter - or to make the lightweight vehicles with a larger front end to provide a greater crush zone for energy absorption.
As opposed to "get rid of these new small cars".
jay, risk compensation doesn't mean that they keep the risk exactly the same. I would expect drivers to only partially remove the extra risk by increased caution.
I don't suppose anyone noticed how 'larger cars' made out in head-on collisions with 18 wheelers?
If there is to be a test comparing vehicles using size as a criteria, I think all vehicles should be included.
After all...fair is fair.
I would expect drivers to only partially remove the extra risk by increased caution.
Fair enough. Though what seems to happen is they quickly acclimtise to the new vehicle and pretty soon are being as aggressive as ever.
, so this suggests that there should be a tax break for minicars to encourage people to use them instead of bigger, more dangerous cars.
Interesting. Pay a tax advantage to increase one's personal risk in exchange for a perceived (not really demonstrated) communal benefit. Would a rational actor make such a bargain?
Bear in mind that it's not usually deceleration that kills someone, it's normally the damage to a body part from collision with some object or from inadequate support. High G-forces make people lose conciousness because of blood pressure effects but I'd expect the G-force would need to be extremely high to cause tissue damage.
That's "injury rate per collision." The USDOT came out in the last couple of years admitting that the whole "SUVs are safer" thing came about because they had been comparing vehicle records on a per-accident basis instead of on a per-passenger-mile basis. It turns out that the road-tanks have more accidents per mile than the smaller cars.
When the DOT released revised numbers, it turned out that the actual risk per passenger mile is at least as good for the smaller cars as for the larger ones.
Props to an academic, BTW, for spending years campaigning to get the record corrected.
High G-forces make people lose conciousness because of blood pressure effects but I'd expect the G-force would need to be extremely high to cause tissue damage.
G-forces that cause blackout (as with fighter pilots) are a couple of Gs (applied somewhat gradually). G forces in a collision can easily be in the hundreds applied very abruptly. Strong torsional forces at the same time can do a lot of brain damage.
There appears to be a tragedy of the commons type of situation occuring in relation to this, i.e. people reduce their own risk of injury at the expense of everyone else by increasing the mass of the vehicle they use. Obviously, to counteract this tragedy of the commons effect, a tax should be put on vehicle mass (and it already is to some degree). Of course, vehicle safety measures that do not increase the risk to other road users shouldn't have any such tax.
When the DOT released revised numbers, it turned out that the actual risk per passenger mile is at least as good for the smaller cars as for the larger ones.
not in the real world
http://www.autoblog.com/2009/04/14/iihs-finds-sub-compacts-fair-poorly-…
the death rate per million 1-3-year-old minis in single-vehicle crashes during 2007 was 35 compared with 11 per million for very large cars. Even in midsize cars, the death rate in single-vehicle crashes was 17 percent lower than in minicars.
[src: Insurance Institute for Highway Safety]
More than a couple to get blackout.
From http://en.wikipedia.org/wiki/G-force :
"A hard slap on the face may briefly impose hundreds of g locally but not produce any real damage"
"Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm."
"Brief human exposure survived in crash[15] >100 g"
Only involving body-part collisions with objects.
How does the brain get strong torsional forces without colliding with some object?
Mercedes C class versus Smart Fortwo: After striking the front of the C class, the Smart went airborne and turned around 450 degrees. This contributed to excessive movement of the dummy during rebound - a dramatic indication of the Smart's poor performance but not the only one. There was extensive intrusion into the space around the dummy from head to feet. The instrument panel moved up and toward the dummy. The steering wheel was displaced upward. Multiple measures of injury likelihood, including those on the dummy's head, were poor, as were measures on both legs.
(from the link by jay)
the biggest problem here is, that some people think that the ["Mercedes-Benz C-Class"](http://en.wikipedia.org/wiki/Mercedes-Benz_C-Class) is a "mid-size" car!!!
ps: i was once called if for an accident with a Leopard II tank. (lucky me, turned out to be an exercise) headline of the day: mid-size cars perform very badly in collisions with main battle tanks!
(firefighters had to lift the tank with air pressure. working below the half-lifted tank was slightly unnerving..)
So basically the problem is big cars.
If the big cars were banned, there would be equality in the momentum stakes, resulting in damage equality.
But you would have more collisions because drivers were less cautious.
Hold on.
Doesn't the big vehicle principle mean that bus drivers and lorry drivers are completely reckless?
Do bus drivers deliberately crash into things because they have such a large vehicle?
Hmmm. Seems to be a slight disconnect there. Like something was read, but not understood.
Hold on. Doesn't the big vehicle principle mean that bus drivers and lorry drivers are completely reckless? Do bus drivers deliberately crash into things because they have such a large vehicle?
please stop this stupid claims. nobody wants to ban utility vehicles that serve an utility.
mom driving tim to the soccer match by SUV does not.
(and yes, i think moving long way transports onto the railway is agood idea)
> Furthermore, because of a effect known as risk compensation, drivers of minicars will be more cautious because they are more at risk in a collision, thus making them even safer for other drivers than the physics of collisions suggests.
Dang it, Tim... this has to be some sort of Tea Party humour I just don't get, isn't it? This just smells like those neoconlibertarian ideas about "personal responsibility" and stuff.
You're just repeating the same numbers that have already been pointed out as inappropriate. Yes, larger cars have fewer fatalities per collision. However, if smaller cars are in fewer collisions (and they are) then the actual risk relationship doesn't track.
The USDOT (even under Bush) finally conceded this point and is now compiling safety data on a per-passenger-mile basis. The results do not favor larger vehicles -- unless you're actually planning to get into head-on collisions.
jay: Are you lying, stupid, or honestly missing the point. Nothing in your quote, and as far as I saw nothing in your linked article, says anything about accidents per mile, or injuries per mile, or risk per mile, or anything else per mile.
So your data - the figure of 35 crashes per million small cars vs 11 per million large cars - is perfectly consistent with the claim that crashes per mile traveled is lower for small cars. And your article's anecdote that there are more insurance claims for small cars is also consistent.
If you relevant have data, I'd love to see it. And your article was so transparently biased it would take, well, someone like you to think it was credible.
How does the brain get strong torsional forces without colliding with some object?
Won't it contact local points inside the skull?
There should be tax breaks to ride bicycles. It's hard to die in a bicycle accident, unless a car or a cliff is involved.
Thanks to my Congressman here in Portland, which has the highest per-capita level of bike commute in the United States, there is here in the US.
Part of the bail-out package (hmm, you'd think a bail-out package would include tax breaks for rowboat commuters, too!)
We recently discussed this at length (Natasha Richardson threads) at White Coat Underground.
Basically, the brain is not the same density as the cerebrospinal fluid around it. The brain is also "tethered" at the brain stem, which is a long way from its center of mass. Any lateral acceleration to the head will cause the brain to twist around on the brain stem, potentially tearing critical blood vessels. Or, of course, "bumping" into the skull. The brain is mush, so even small impacts do Bad Things.
Either way, you get intracranial blood loss. That blood has nowhere to go since the skull is inflexible, so the intracranial pressure rises and interferes with blood supply to the brain.
There's a lot more to it, but all in all it's a Bad Thing.
>There should be tax breaks to ride bicycles. It's hard to die in a bicycle accident, unless a car or a cliff is involved.
Well here in the UK, some car drivers think cyclists are pedestrian killers.
But really their main gripe is that cyclists aren't required to have insurance or pay road tax.
That's rotational, not torsional. The brain rotates about the neck on a horizontal transverse axis with the rest of the head.
As I've been suggesting all along, the head needs to hit something to suffer Bad Things.
Large vehicles are a menace to smaller vehicles. What gives SUV drivers the right to endanger less massive vehicles? Tragedy of the commons, indeed. Driving should not be a pissing contest. A better solution is smaller vehicles for those who require independent transport, and mass transit for the hordes of commuters. Urban planning must figure into the discussion, too. If I live close enough to my workplace, I''m walking to work. We could reduce traffic fatalities with better urban design.
These simple minded comparisons are meaningless. Where's the linear , logistic regression adjusting for all relevant variables ? I think the main point about urban transport is that you don't have to go faster than a mean speed of 40 km/h to have exactly the same personal transport system as we have now,
I agree with the idea but I think that rather than a tax concession on the vehicle there should be a tax impost on the insurance charges vehicles should be required to pay if they are a heavy vehicle. Smallere vehicles should also be taxed but less so.
When two cars of equal size collide the total damage is approx 2D where D is the damage to either car. Since (in the US at least) about 70% of accidents are two car collisions this suggests an average traffic accident externality of around 70%. So people drive excessively given the risks they impose on others. The best solution to this is to tax insurance premiums to capture this. People will drive less and the externality gets internalised.
If a big car hits a small car the big car gets off lightly and the little car cops it severely. Now the big car imposes a really large accident externality and the small car a much smaller one. Internalising the externality by encouraging less driving will occur by insurance premiums on big cars being really punitively taxed and on light cars being lightly taxed.
These types of taxes are not very popular and so are often approximated by using distance related insurance charging.
The same principle applies â if you drive a weighty 4-wheel drive or a B-double truck your premium per kilometre should be much higher than if you are driving a small car.
What about people who have "legitimate" need for a big vehicle, like construction workers, landscapers, hunters, etc?
Ben, that accounts for a small fraction of the number of oversized vehicles on the road. And when construction workers and landscapers are off doing their job, they're typically not getting wasted and drifting across the center line, drunk driving being a factor in a large number of accidents including head-ons. (obviously, a drunk driver in a small car might wander into the path of a worker's truck).
Most of those people are driving pick-ups, not SUVs, which by definition are designed for non-work use. How many hunters stuff a bloody deer carcass into the back seat of a leather-upholstered land rover?
Re/ high accelerations and duration:
The qualities of an acceleration profile most predictive of brain injury have been reduced to a formula called the Head Impact Criterion (HIC). Interestingly for the present discussion, the experimental data most used in developing this number came from Mercedes crash tests. I did some simulations for a medical implantable a few years back, and was struck, as it were, by the importance of peak acceleration. So -- yes, you can experience hundreds of Gs for a few milliseconds in a crash, and that (not the duration) is what kills you. That is also how airbags and helmets save lives: by spreading out the duration of a deceleration event.
Jay remarks that "your theory would suggest that motorcyclists would be an extremely cautious group" and seems to regard this as an argument against risk compensation generally. I can testify from experience that most motorcyclists are in fact extremely cautious, and that they are more cautious when riding than when driving. The likelihood of sustaining an injury on a motorcycle is much greater than the likelihood of inflicting one, a fact reflected in motorcycle liability insurance rates. Do some still take risks, and get injured or killed? Sure, but on the whole the effect of exposure is to increase caution.
I don't know. The guys at Top Gear smacked a remote controlled Smart car into a 20 ton barrier at 70MPH. There was barely any deformation of the passenger cabin.
However they did mention that while the car itself wouldn't crush you, the massive deceleration would. Almost forgot to mention, the car MOVED the 20 ton barrier.
Don't know about what? That a head on collision at 70MPH just might kill you?
Most of those people are driving pick-ups, not SUVs, which by definition are designed for non-work use. How many hunters stuff a bloody deer carcass into the back seat of a leather-upholstered land rover?
True, most use trucks. On the other hand, I used to have an SUV that I used, and I had an attachment for the trailer hitch that would carry the deer or whatever. And SUV is more convenient for family life on those days when I'm not up in the woods. Which is most of them.
And if need had been, I would have put a tarp down and stuffed the bloody deer carcasses into the back (not the back seat) of my Explorer. Most hunters don't drive fancy-lad land rovers.
Simple question: Which car do you want your wife and your kids driving around in? Minicar or SUV?
> Simple question: Which car do you want your wife and your kids driving around in? Minicar or SUV?
Bus.
Next question?
I love it! It's safer for the people in the bigger car, LOL!!!!!!! That's classic.
I don't work trauma, but from what I've heard injuries to large, highly vascular organs - such as the spleen or liver - are quite common with violent load factors. They are heavier than surrounding tissue and will move farther given the room to do so. Kidney damage can also occur. The large vessels can also suffer. I believe jre is right on peak acceleration. Even if the brain is protected, any load factor in excess of 100g's is bad news.
>Simple question: Which car do you want your wife and your kids driving around in? Minicar or SUV?
If everyone owned SUVs, there would be no 'advantage'. There can only be an advantage if there is a difference.
If the market was saturated because people used your logic, then manufactures would have to develop a more robust vehicle.
So if you were only concerned about yourself, the logical next step would be to own some sort of armoured car.
and so on.
Therefore at some point people will organise a 'nanny state' that would have to halt the escalating 'arms race' of 'family' road vehicles.
What does this tell us?
There can be no good result from only considering yourself and your family. Logically at some point, people will organise themselves into communities and create 'nanny states' that would restrict individuals.
That's life!
Or more precisely, any load factor in excess of 100g's for longer than 10 milliseconds is bad news, according to the formula for Head impact criterion (HIC).
For example, stopping at uniform deceleration from 70 MPH in a distance of 1.1 metres requires 45.5 g's of deceleration for a period of 70 milliseconds, giving a HIC of 980. There would be nearly an 18% probability of a severe head injury, a 55% probability of a serious injury and a 90% probability of a moderate head injury to the average adult.
Of course, stopping from the same speed over a distance of 2 metres is quite survivable considering it can have an HIC of 400.
What Paul said.
The greatest safety device in any car is the nut that holds the steering wheel. Encasing yourself in armour only works for so long. I have driven small (by American standards) cars for all my driving life and have never thought that in an accident that the car would save me.
I used to ride motorbikes. Those motorcyclists that survive beyond 2 years or so develop the idea that every other motorist on the road is out to kill them and usually ride accordingly. I tend to take this into account when I drive in a car. However dumb mistakes in a car, that I make more often than I would like, often do not lead to death or disablement because a car has more protection. Drivers of cars can make more dumb mistakes than motorcyclists and survive.
The idea that small cars are more dangerous is just plain wrong. The notion comes from, as other commenters have noted, the size differential makes smaller cars in comparison with larger cars appear more dangerous however when the size difference of larger and smaller cars is less extreme such as here in Australia the fatality figures are roughly the same. If larger cars are safer then America with its predominance of larger cars should have lower fatalities which is doesn't.
There are so many other factors at work such as alcohol, excessive speed, road conditions and weather conditions that make up the reasons that car crashes happen and who survives that vehicle size is usually the last thing considered.
Comparing a Mercedes to a Smart is also just wrong. Given that both of the cars are rare on Australian or American roads what are the chances of either of these cars colliding? As small cars are amongst the most popular cars in Australia you are far more likely to have roughly the same car colliding with you so then the ANCAP testing will tell you that small cars are just as safe as a larger car with many larger cars not having 5 stars when some of the smallest cars do.
Most of the time it is SUV owners desperately trying to justify their Toorak tractors that trot out these studies. Real off-road vehicles are very rare even here in Perth - you know the ones with red dust caked on them. My favourite thing is when I travelled to Kalgoorlie I saw less 4WDs in the main street there than I did before I left in West Perth where all the plastic surgeons have their offices. Hunters do not buy many 4WDs in Australia unless they are hunting money and influence amongst people that are easily impressed and imagine that a large car means wealth and prosperity.
For those of you in Perth just go down to Black Tom's there and count the 4WDs.
Simple question: Which car do you want your wife and your kids driving around in? Minicar or SUV?
Idiotic question.
If you really care about your wife and kids (nice sexism there), you should become an 18 wheeler operator and never let them leave the vehicle. Also, no bicycles for the kids. Or walking. You really need to move into a bomb shelter. That is, if you really care about your wife and kids.
This idiocy has been pretty well dealt with by Thomas Wenzel and Marc Ross in the American Scientist
RTFR
A slightly off-topic diversion here:
According to a piece over at the LA times web-site, Hummer drivers receive over 4 times as many traffic tickets per mile than does the average driver. Lest one think that the Hummer's greater profile/visibility, rather than the driver's behavior, is responsible, the LA Times piece noted that the Scion was #2.
The conclusion was that Scion drivers are generally younger, less experienced and immature while Hummer drivers are generally older, more experienced, and immature.
Note: Here's the full URL for that LA Times piece: http://latimesblogs.latimes.com/uptospeed/2009/01/hummers-tops-in.html. I tried embedding the URL as a link, but this site's software insisted on appending a "nofollow" tag to the URL (probably to discourage google-ranking spammers).
Which reinforces one of the recommendations of the insurance industry report cited by the Times article: build lighter vehicles with larger crush zones.
Not really, as one of the report's recommendations rests on exactly what you cite:
Unfortunately the article focused on the crash results, with the report's recommendations getting a brief mention at the very end.
The take home point is that the Smart car isn't as smart as it could be ...
Being against minicars because of higher potential lethality assumes that everyone else will be driving a big tub. The solution is more minicars, not fewer.
hc: You suggest a tax on insurance premiums for heavy cars. I would suggest instead a fuel taxation (increase) as heavy cars tend to use more gas per mile driven. Surely it would be easier to administrate. I believe the all US states already have gasoline taxes.
dhogaza they managed to bury it pretty well, which leads Eli to conclude that they meant to do so.
I loved "Family Guy's" take on Hummers -- Peter asks, "What kind of guy drives one of those?" Cut to some twenty-something maniac in the cab of a Hummer, going "Wow! I'm so high up! The other cars look like toys! Wow! This is great! This makes me want to merge without looking!"
I fault the reporter, though, not the industry report.
From the point of view of the people who put it together, I would think that they'd believe the focus should be on the recommendations, because after all that's the real point of doing a study. Of course their other major recommendation - lower speed limits - is probably politically unfeasible. Note that they did not recommend "don't build smaller cars".
But for whatever reason, the reporter decided to give it a sensationalist spin. Of course the crash tests yield attention-grabbing photos, while "reduce speed limits" does not ...
The key to talking to reporters is to have a single message and never say anything that steps on the message as in "the take home from this study is that we can build safer cars" as in "Do heavier cars win in a crash: Answer: Well engineered smaller cars do better in crashes than heavier larger ones"
Yeah, if the reporter ever bothered to talk to them ...
I thought it was an odd article all around. The headline could've easily been "teensy cars survive crashes much better than you might think", since I imagine most people assume they're total death traps. Which they aren't.
What makes this factoid only marginally relevant is the low frequency of crashes which are headon or near headon at any substantial speed, particularly here in the US where highspeed roadways tend to be divided. Most collisions between cars are either a sideswipe by a car changing lanes or a rear ender when the front car slows more than the rear car, both between two cars with relatively small difference in velocity, or a sideswipe by a car in the opposite lane or a t-bone when turning across traffic, at lower speed. The last case is the one where the difference in mass of the one car is most likely to make a difference; but off the top of my head I cant see that being struck in the door next to you by a lighter car while your vehicle remains fixed is that much worse than being hit by a heavier car which carries your lighter but well designed and rigid vehicle along with it. (Happened to me; making stupid turn in compact, was hit in vicinity of passenger side front wheel by normal size pickup truck, both of us at normal city street speeds; truck pushed car across three lanes to the opposite curve. In apparent conflict with the finding in question here, I was completely uninjured although my lighter vehicle was totalled, the driver of the heavier truck, which drove away without any problem, must have been terribly injured, as he later got paid $10,000 by my insurance company for "soft tissue damage", which I learned when time came to renew my insurance.)
But anyway, around here at least, most fatalities are single vehicle crashes, either rollovers where somebody is thrown from the vehicle (usually a highschooler in a jeep type of thing) or a crash into a tree, light pole, abutment, wall, building, guard rail, ditch, etc. (usually in the hour following closing time for bars).
I did a project analyzing crashes and injuries for the state here; although the police form has spaces for "first object struck" and "second object struck", the state database kept only the first object struck. I was therefore able to prove the surprising finding that the most lethal object struck was apparently the curb.
z if you read the Am Sci article Eli pointed to you will find that SUVs and pickups are killers in T bones because of their frame which forks the other car. Changing that design alone would increase crash safety enormously.
They weren't testing at highway speed - the insurance people aren't dummies (though they use a lot of them in their crash testing).
Head-on crashes cause a lot of injuries or even death at relatively low speeds since, after all, two cars hitting head-on each going 25 mph is equivalent to hitting a stationary object at 50 mph, all things being equal.
T-bones are bad, too, which is why safety engineers focus on this problem, too.
I live a few blocks from a large auto repair facility and walk by it almost daily coming home from my morning coffee excursion. Each morning there's typically one or two wrecked cars left at the side of the road next to it by a tow truck. I'd estimate about 1/2 of them appear to be head-on collisions, front smushed in, airbags deployed.
"Head-on crashes cause a lot of injuries or even death at relatively low speeds since, after all, two cars hitting head-on each going 25 mph is equivalent to hitting a stationary object at 50 mph, all things being equal."
uhuh. for each car, hitting an immovable object or an identical car at an identical speed in the opposite direction is identical. our freshman physics class, first term. of course, for both cars, the total energy absorbed is double the one car case.
tbones are bad for intrusion. side airbags help a lot. as discussed, the human bod takes a good deal of acceleration before getting seriously damaged, provided the force is distributed. head torsion, whiplash, etc. is a result of the head being improperly supported at the time of impact, which is, of course, tautologically. you can get your jaw broken and still remain conscious, but a relatively minor punch can knock you out or worse, if it rotates your head relative to your neck.
somewhat off topic, in japan they require tractor trailers etc. to have a fence extending below the trailer frame to prevent cars from underriding and the driver getting beheaded. in the US, of course, we have a more enlightened attitude, so that if you wish to you are free to do so.
Yes. So why do you think safety engineers focused on relatively low-speed head-on collisions first? Would it have to do with the fact that doubling the relative speed of collision releases more than a doubling of energy to be dissipated?
Sure, who argues against more safety engineering? Are you suggesting that because the insurance industry lobbied for years for mandatory seat belts as standard equipment in automobiles (I do hope you understand their role in this ...) that this means they oppose fence guards against underriding of passenger cars when you rear-end a truck?
Somehow I doubt they do ...
Look, it's obvious that the insurance industry lobbies for increased safety for one reason only: increased profits.
But it's equally obvious that some of their lobbying efforts have been successful and have saved lives.
Ignoring the fact that I don't want my kids driving any car just yet, the car that can stop.
PeterBP has a good point. Large heavy vehicles used as regular transportation need more gas for no good reason. Owners should pay more per gallon than those of more efficient cars. They artificially increase demand (hence driving up prices) and do not get anything more accomplished with the extra fuel used. Me paying the same as they are amounts to me subsidizing their use of an inefficient vehicle. The ones with a true legitimate use will have some sort of professional license to show and can pay regular price. For the rest of them, since they're mainly looking to boost their egoes, they can shoulder the cost of it themselves, I'd be glad to be dispensed from sharing in it.
Actually, the effect of vehicle mass on fatality risk in collisions between vehicles of equal mass (phew, what a mouthful) has been studied by a few people, if anyone wants to follow it up properly:
Grime and Hutchinson (1979) DOI: 10.1080/00140137908924592: Effect of mass in car-to-car crashes where cars of equal mass: negligible
Wood and Simms (1992) Accid Anal Prev. Jan;34(1):93-9.: The relative injury risk between pairs of similar cars (i.e. a pair of smaller cars compared to a pair of larger cars) is inversely proportional to the ratio of car mass. The relationship is fundamentally due to the size of the cars.
So is seems that mass ratio is important and size is important (for safe energy absorption).
Also google Leonard Evans for a host of other articles on this subject.
But, as previous post(s) pointed out, there are many more popular ways to be killed and injured other than in car-to-car head on crashes, and the effect of mass in these kinds of crashes remains to be fully determined - this is especially important in single vehicle crashes. A problem has been that 'heavy' might have been a proxy for 'safety features and high strength steel' in older vehicle models (or even now), and so statistical studies of single vehicle crashes showing a benefit of higher mass might suffer from confounding. (Although there are obviously physical reasons why high mass in such crashes could be beneficial).
Just out of interest, crashes in Australia cost the economy around $15billion per year.
Chz
Robert
"Would it have to do with the fact that doubling the relative speed of collision releases more than a doubling of energy to be dissipated?"
nonono. you aren't doubling the velocity; you don't have one car (or two) moving at (2*V) to give .5*M(2V)^2 (or .5*2M(2V)^2, however you look at it; either way its wrong) instead of .5*MV^2.
"relative" velocity is the problem. relative to what? in the "stationary" frame of reference, where the crash is symmetrical, the same frame where you had the one car hit the stationary brick wall, nothing is traveling at double the velocity; both speeds are relative to the stationary frame, they are V and -V. since velocity is squared, the fact that one car has the opposite sign on the velocity is irrelevant. what you have is twice the mass, each traveling at the same speed, V. Thus .5*M(V)^2 + .5*2M(-V)^2 = .5*2M(V)^2 =MV^2, double the single car brick wall case, dispersed into two identical objects of equal mass, so that each car experiences the same stress as the one car into the brick wall model.
in order to have the "combined velocity" be double, you'd have to be in the stationary frame of reference of the oncoming car, replacing the brick wall; in that frame of reference it is standing still and the velocity of the oncoming car is 2V. Total kinetic energy .5M(2V)^2=2MV^2, 4 times the brick wall model. but that frame of reference is moving relative to the "stationary" frame of reference, so that the results after the crash are not stationary in that frame; instead, you end up with both cars, total mass 2M, moving "forwards" at half the initial "combined" velocity, or .5*2V, accounting for .5*2M(.5*2V)^2 =MV^2 of the initial kinetic energy, precisely 1/2; leaving a net kinetic energy dissipated of 2MV^2-MV^2=MV^2, double the single car model, dissipated into two cars, as explained above.
You need to fix wikipedia then:
Head-on collisions are an often fatal type of road traffic accident. U.S. statistics show that in 2005, head-on crashes were only 2.0% of all crashes, yet accounted for 10.1% of US fatal crashes. This over-representation is because the relative velocities of vehicles traveling in opposite directions is high. A head-on crash between two vehicles traveling at 50 mph is comparable to a vehicle traveling at 100 mph striking a stationary vehicle.
which is nowhere near as severe as a vehicle traveling at 100 mph striking a practically immovable object like a tree or a building.
Aren't car companies 'nanny commercial corporations' pandering to the desires of the individual?
Babies crying, ah that's OK, just give baby a nice new car. That will shut baby up. Then baby gets older, they become obese. Ooops, maybe we should have had a different nanny.