As automobiles get heavier, even small velocity variations matter in a crash

An orange Volvo SUV after a crash test.

Enlarge / A Volvo XC90 SUV following a crash take a look at in Sweden. (credit score: Jonathan Gitlin)

On the finish of January, security researchers on the AAA Basis for Visitors Security and the Insurance coverage Institute for Freeway Security printed a examine exhibiting that small will increase in velocity have large penalties throughout a crash. After crashing three equivalent automobiles at rising velocity, the examine confirmed {that a} automobile that aces the take a look at throughout the board at 40mph (64km/h), with only a 15 % change of great damage could get a failing grade general, with a 59 % likelihood of great damage at 50mph (80km/h). At 56mph (90km/h), the end result was even worse; the 50th percentile male crash take a look at dummy solely had a 21 % likelihood of escaping critical damage or worse.

Little doubt, the truth that automobiles are designed to move a 45mph (73km/h) crash take a look at and never one thing at freeway velocity has one thing to do with the outcomes of the examine. But it surely’s additionally a reminder of primary physics: a car’s kinetic vitality is the same as half its mass multiplied by the sq. of its velocity. So, the common US light-duty car—which weighs about 4,000lbs (1,814kg)—has 11.2kJ when it is touring at 25mph (40km/h) however 22kJ at 35mph (56km/h), a truth that folks can use subsequent time somebody complains that metropolis velocity limits are too gradual.

However velocity is, actually, solely a part of the equation. Native authorities can set limits on how briskly we will drive, however nobody’s going to cease you shopping for a 5,000lb (2,268kg) automobile as a substitute of a 4,000lb one. And massive automobiles are enticing to most of the people. Mockingly, a lot of this development is fueled by the truth that security sells, and the largest, heaviest automobiles are the most secure—for his or her occupants, at the least. Pedestrians or individuals in older or smaller automobiles? Not a lot.

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