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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."
Driving fast in an SUV loaded with kids is about as unresponsible as it gets, I see it quite often though...
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The goal of this safety feature isn't to influence where the pedestrian hits the car but how. By the time the pedestrian hits the hood, it must already be lifted. Then it provides an extra few inches of collapsible zone before the weight of the pedestrian meets the innards of the engine compartment, thereby tremendously reducing the maximum force of impact and risk of injury to the pedestrian.
Increases in that sort of safety may decrease insurance premiums which may make people consider them more. It probably won't be a major consideration though but such features do tend to become more standard over time.
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I'm learning to drive, and people who treat indicators as an optional extra are nothing more than life threatening. It's difficult enough for me to try keep tabs on everything I should be doing, what other people are doing, and what the road markings tell me to do without some asshole merging lanes without indicating.
As for the mostly males involved in crashes, it's the same statistical nonsense as mostly red cars are involved in crashes. It's simply because there are more males on the road to be driving dangerously. Insurance for me (18yo Male, learning to drive) is phenominal even on a low power car. Fortunately I plan to do a Pass Plus (An extra test for additional road skills) so it should drop, but your comment about subsidising the idiots still holds true even then.
How many people can read hex if only you and dead people can read hex?
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
AccountKiller
The UK has seen an explosion in the numbers of people driving around in ridiculously proportioned vehicles. America has lived with them for decades so your cities are built around them. The UK is not. Parking spaces are a lot smaller.
I was waiting outside a supermarket the other week, in a parking slot, and one of these tossers shows up and stops in front of me to let out his passengers before moving into a space. The reason was obvious. His car was too damned big to get the doors open properly when it was between two other cars. As far as I'm concerned he should expect to have his bodywork smacked up by the car doors on either side of him.
I also always make a point of thanking people for waiting on narrow roads where parked cars make it impossible for two cars to pass eachother, unless they're driving something like a VW Touraeg. If it is possible for two normal cars to pass each other and your stupid truck sized car is making it impossible then it's your own fault and you'll get no thanks from me. If you drove a normal car you'd have had no reason to stop.
I find it amusing when the vehicle is blamed rather than the operator.
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.
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.
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!"
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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.
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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.]
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.
You're right in a generic sense, but the fact that cars don't have elastic collisions changes things.
Also, its important to consider deformation fo the passenger "cage" to be almost as important. A lot of light trucks/suv tend to have signficant instrusion into the footwell and "A" pillar in offset front collisions making them less safe than they first appear.
On the other hand, if you have a 5000 pound SUV hitting a 2000 pound minicompact, I don't have to be Newton to figure out the result.
But in reality, most new cars weight closer to 3500 pounds, and most SUV's are probably around 4000, so despite looks, there's less of a difference than it appears. Combine that with the fact that many cars have more sophisticated crash zones than SUVs and far less tendency to roll over, and you get that a car can be far safer than an SUV.
Personally, I'll take my changes in my BMW rather than a Ford Explorer.
SUV = Sport Utility Vehicle
Sport = off road
Utility = Carrying or towing capacity
Off road use requires a higher center of gravity to allow clearance over hazards, the ability to cross over ridge crests without scraping the undercarriage, etc.
Carrying capacity and towing capacity requires both additional cubic cargo space, weight and power. SUVs are used for towing boats, trailers, campers, etc., and need these additional characteristics to be successful.
All of this is expensive. A typical SUV starts out at the dealership at over $25K, with most coming in at over $35K once you add the additional towing packages, etc. Many come in at over $45K!
If a family camps, boats, or participates in other off road activities, an SUV is often a necessity. But at that expense, many people can't afford both an SUV and a regular car. So they buy just the SUV, or they can afford just one additonal car, so Hubby drives the lower gas milage car to the more distant workplace, and Soccer Mom drives the SUV around town cause thats all the cars they can afford.
At least in the US, the government doesn't have so much power that they can just ban a particular vehicle without political consequences. Not when it's as popular as the SUV. The recreational lobbies would eat them alive.
It's only a very small minority of folks that just buy an SUV as a status symbol.
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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.
When I am king, you will be first against the wall.
"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.
evil is as evil does
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...
And the trucking industry constantly lobbies for greater weights for their trucks. Which cause lots of wear and tear on the roads if nothing else. But now they can't stop as quickly, and they can't get out of their own way on a hill, resulting in mini traffic jams and high speed differentials, which are a dangerous situation.
"All of this is expensive. A typical SUV starts out at the dealership at over $25K, with most coming in at over $35K once you add the additional towing packages, etc. Many come in at over $45K!
Actually, SUV's might be expensive at the dealership, but they are very cheap to produce, hence the extreme profitability.
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What I propose is that all vehicles that are not commercially owned (that is a separate issue) be grouped together. No distinction between the fuel consumption and crash standards for cars versus pickups & SUV's. Rate them all on the same scale, provide the same penalties to anyone who violates the accepted standards. If we applied the same standards to pickups that we do to cars, most would cost a couple thousand dollars more from the gas guzzler tax. And that is how it should be, no special priviliges to anyone.
Remember that one of the main reasons that SUVs were sold was that they exploit loop holes in pollution, safety and fuel efficiency standards. They are by their very nature low quality vehicals.
Minivans were the same way until too many people were killed and the rules tightened. If you take a close look at modern minivans they are essentially reinventing the station wagon.
Instead of exploiting loops holes, non-US manufacturers developed hybrids and high efficiency vehicals. SO now while US car companies are in trouble, foreign car companies are gathering up more market share. Just another sign that US business leadership is screwed. No vision, no intelligence, no ability or concern that we have known that world oil productuion would peak about 2005 (we have known this for about 30+ years). Just business as usual, play golf, out source and go for the short term.
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I like the idea, but sadly, it won't work here. Where I live, the jackasses in the giant suvs with "W" stickers just take as many parking spaces as they need. That is, when they're not driving around yelling unintelligible epithets at bicyclists.
I am not a crackpot.
If a family camps, boats, or participates in other off road activities, an SUV is often a necessity.
That's bullshit. My family went camping and boating dozens of times and has never owned an SUV. The SUV wasn't mainstream until the 90s.. you think people didn't camp and go boating before then?
However, I have seen countless news reports ("SUV crashes into schoolchildren") that imply that the vehicle caused the accident/collision/etc. of its own volition. On the other hand, when it is a subcompact or sedan, the report generally correctly places the culpability on the the responsible driver.
If I understood your message correctly, you believe that the very existence of SUV's/light trucks on the same road as any other vehicle is a safety hazard on the same scale as the removal of seatbelts and the installation of "impaling spikes". On the other hand, my opinion is that an unsafe driver is a safety hazard to self and others regardless of the vehicle driven. (Although certainly more damage can be done with a vehicle of greater mass.)
The plural of anecdote is not data. Your individual experience does not indicate that this study is flawed.
Short version: you were lucky.
Sean
Did you RTFA? Unibody cars are much, much safer than body-on-frame cars because the unibody construction permits the car to deform and absorb the force of the collision where a rigid frame exposes occupants to the full force of the collision.
The "problem" is not cars moving to unibody - the improved safety and fuel economy drove that - the problem is millions of drivers using "light" trucks as their day-to-day vehicles, with no requirement that these trucks be designed with passenger car collisions in mind.
The good old days weren't as good as you say - body-on-frame collisions (such as the one I experienced in my dad's '74 Buick Centurion) were horrible compared to unibody-to-unibody collisions (such as the collision my wife experienced last month in her Hyundai Elantra.)
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.
My opinions are my own, and do not necessarily represent those of my employer.
You're right. A place calling itself the "Parners for Child Passenger Safety" is going to be very biased, but biased towards keeping children safe.
Is there any reason to think that they would be biased either for or against SUVs? I can't think of any reason. If you see one, please explain.
Perhaps you own an SUV and don't like the implications?
...by driving at a reasonable speed, and not causing sudden steering inputs.
Collisions sometimes can *not* be avoided.
Thanks, I'll stick w/ my Dodge truck.
Thanks for your concern, though.
That will never fly. You do realize that body on frame vehicles are the only correct way to tow large boats and RV trailers, right? While I don't disagree that CDL's should be required (in most states they are not hard to get and in some states, are required for class a motorhomes), requiring commerical insurance so that a family can take a vacation seems a bit extreme.
So if we follow that logic should motorcyclists pay the least insurance, since from a damage to life and property motorcyclists face the greatest danager in any collison. Or you could flip it around and since motorcycles are lighter and in collisons they (or the riders) tend to become dangerous flying objects, perhaps we charge them more?
Also I won't argue that body on frame vehicles cause more damage to other vehicle(s), but you have to base libility premiums on whose at fault more often, and I have to think, based on the rates, that body on frame vehicles are at fault less often. Of the five vehicles I insure, two are body on frame, I pay more in libility for the unibody vehicles than the body on frame, which tells me that some statistics must show that unibody vehicles are at fault more often.