Peter Cheney
From Tuesday's Globe and Mail Published on Monday, Oct. 19, 2009 8:44PM EDT Last updated on Wednesday, Oct. 28, 2009 2:28PM EDT
What happens when your van gets hit in the side by a vehicle doing 200 kilometres an hour?
The short answer: You will die.
“That's not a survivable collision,” says Amrit Toor, an engineer and accident-reconstruction expert with Vancouver-based Intech Engineering. “The forces are monumental.”
As experts like Mr. Toor know all too well, a car crash is governed by the immutable physical laws that Sir Isaac Newton first articulated in the 17th century.
And speed is a killer, because the force of a collision rises as the square of the velocity – which means that even though the speed is only four times higher, a crash at 200 kilometres per hour is 16 times worse than one at 50 kilometres per hour.
In a collision, a car's kinetic energy is dissipated in two ways, which engineers refer to as damage and displacement. The car, as well as the one it hits, loses energy as components bend and break. Energy is also dissipated by friction as the force of the collision pushes the impacted car along the road.
Excessive speed creates risks that few non-professionals would anticipate. A car doing 200 km/h, for example, sets the stage for what traffic engineers call an “unalerted reaction.”
When we encounter something outside our typical experience, we react slowly, or not at all. When we see an oncoming car, for example, we judge how much time it will take to reach us based on typical speed patterns.
At 70 km/h (the posted limit on Finch Avenue) a car 60 metres away would arrive in just over three seconds, giving enough time for a left turn. But at 200 km/h, the car would reach you in one second, making a collision almost inevitable.
“It all comes down to math,” says Constable Hugh Smith of the Toronto police traffic services unit. “At 200 kilometres an hour, you are a projectile.”
This weekend's crash also illustrated the vast differences that angle and position can make. The driver of the BMW (who faces criminal charges) was the lucky one: because he hit the van going straight ahead, he took advantage of several lifesaving features.
His seat belts and air bags restrained him and slowed his deceleration. His car's kinetic energy was absorbed by the crushing of its front compartment, and by the destruction of the van that he hit.
The passengers in the van, on the other hand, faced a worst-case scenario. The speeding BMW hit them in the side, where there is little structure to absorb an impact through deformation. “It's the worst way to get hit,” Constable Smith says. “You don't have much of a chance.”
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