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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."
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?
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.
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.
I am officially gone from
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.
The "Civilized World" jumped the shark ca. 1973.