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Speed and its Effect on Car Crashes

Does speed really kill? You’d be surprised how much a few mph makes when it comes to car accidents. By making small changes in vehicle and impact speed, the outcome of a collision can change dramatically. Here’s what you need to know about speeding, accident protection and new vehicle features that slow your vehicle before impact.

Calculating Force: Why Speed Kills

To calculate impact force (F), you would use the following formula:

F = m * v²/ (2 x d)

m is the mass of the object
v is the speed of the object before impact
d is the distance traveled during the collision

See that little “2” by “v”? That means “v” is squared or multiplied by itself. In a crash at 50 mph, this would be calculated as 50 x 50 = 2,500. Going 100 mph? 100 x 100 = 10,000. Even though the speed only doubles, the impact force is four times as high at 100 mph as it is at 50 mph.

Let’s say you’re an average adult male. You weigh 195 lbs. You’re in your car, wearing your seat belt, when you have an accident while traveling at 30 mph. Your body experiences an impact force of 4.5 tons.

Let’s take the same situation, but you’re in a little more of a hurry. When the accident happens, you’re going 35 mph instead of 30. Now your body experiences an impact force of 6 tons, 50% more than before. What was a serious accident is now likely to be fatal. Of course, this is assuming you don’t have any protection. This is where your vehicle’s safety features come in.

Crash Structures: Buying You Time

If you jump up and down on the ground, you’ll start feeling the impact in your knees and legs pretty quickly. However, if you jump on a trampoline, you’ll feel very little fatigue. As you land, the fabric of the trampoline stretches, extending the time of impact. This turns what would be a sudden jolt into an extended, low force impact.

Crash structures in modern cars work the same way. The parts of your vehicle beyond the cab, including the engine compartment and trunk, are designed to crumple on impact. This increases the time of impact, reducing peak force. As a result, you’re more likely to survive the collision. Effectively, your car is designed to sacrifice its front or rear end to protect you.

Seat Belts: It’s Not the Speed, It’s the Stop

Seat belts also help spread out the impact. The primary purpose of a seat belt is to stop the wearer with the car instead of letting them fly forward into the dash, steering wheel and windshield. If the seat belt had no stretch, it would make the stopping distance as much as 5 times as long as a stop with no seat belt.

By adding some stretch to seat belts, designers are able to increase stopping distances even more. In an impact where the car goes from full speed to a stop in 12 inches, the added stretch can increase the distance to 18 inches. In turn, impact forces are one-third lower.

Of course, that’s not all a seat belt does. By keeping your body centered, you’re aimed directly at air bags and other energy-absorbing surfaces, further reducing impact. If you don’t wear a belt, the air bags still work, but they have to deploy faster and may hit you off-center, making them less effective.

Automatic Braking

The sooner you can slow down, the less destructive the accident will be. This has led manufacturers to add automatic braking systems that can react faster than we can. The Insurance Institute for Highway Safety (IIHS) collected data on collisions with and without automatic braking and forward collision warning systems. They found that the chance of a rear end impact decreased by 50% if the following car had these two safety systems. Even if it doesn’t bring your vehicle to a complete stop, by reducing your vehicle speed, the impact force decreases dramatically.

While early systems were notoriously buggy, designs seem to be improving. Consumer Reports recently asked their subscribers to report their experiences with these systems. Overall, 81% of owners were satisfied. Some brands, including Genesis, Lexus and Tesla, were praised by owners for their systems. However, owners of Acuras reported overactive systems, while Mazda owners said their cars apply the brakes harder than needed.

We Make Collision Repair Less of a Headache

Even if you’re unharmed after an accident, you still have to deal with collision repair. Merton Auto Body makes it easy. We’re an I-CAR Gold Class certified shop, and our technicians are ASE certified. That means we have the latest training and techniques for repairing everything from antiques to the latest models. We’re located near the Ironwood golf course, so we’re a short drive or tow away from Pewaukee, Lisbon and Hartland.