Between You And The Crunch: Your Car's Crush Zone

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Everything you need to know about the crumple zones on a car and how they promote safety

Read in this article:

What are Crush or Crumple Zones?

Car crumple zones - also called crush or crash zones - are often mentioned in car reviews and sound quite dramatic. But what are crumple zones actually, and what are they designed to do?

Crumple zones are designated areas on your car that are designed to deform and crumple in an accident to absorb some of the energy from the collision, in order to protect the occupants. While we may assume that there are only two of these, namely the front crumple zone and the rear crumple zone, the side structures on your car are also considered as crumple zones. The entire car cannot act as a crumple zone as that would mean the occupants are crumpled too - so, a rigid frame is built to surround the occupants, with dedicated zones that will crumple under force.

The way these designated zones are designed determines how well the car's structure performs in a crash and how well it protects its occupants - so exactly how do crumple zones work?

Crash Tests Mercedes-Benz

How do Crumple Zones Work?

First invented and patented by Mercedes-Benz engineer Béla Barényi in 1937, crush zones in cars are designed to progressively crumple and deform to absorb the kinetic energy of a crash, slowing down the vehicle as gradually as possible to reduce the deceleration forces on the occupants. The front crumple zone is the main focus of crash safety and the dynamics of this crash section must be precisely designed, the physics involved well understood, and the crumple-zone materials used to build these structures carefully chosen for the deformation to happen as planned.

Basically, when a car is involved in a collision, the force exerted by the impact can be harmful and even fatal to passengers. The aim of crumple zones is to reduce the initial force, and redistribute it before it gets to the passengers. But, the various mechanical components on board pose a problem - if the front end is a crumple zone, what happens to the engine in a head-on collision? Designers have to find a way to ensure the engine does not get pushed back into the cabin as a result of impact. Similarly, in rear-end accidents, the frame should bend away from impact and lift the gas tank out of the way.

Think about the work that goes into a design such as this - naturally, with larger cars, there is plenty of room to build in crumple zones before the passenger area is reached. But achieving the same thing on compact cars is much harder, with developers often having to ensure transmissions, tires, wheels, and suspension are also designed to deform or absorb kinetic energy.

How to Choose a Safe Car

All new cars sold in the USA have to conform to certain minimum safety standards, and equipment such as ABS brakes, stability control, and a backup camera are mandated by law. However, there are other criteria, too, not just the bare minimum required by law. So, how do you choose a truly safe car for you and your family?

These are the most important criteria:

  • Passive safety features: A car's passive safety features help you survive a crash once it happens. Chief among these are the crumple zones, seat belts, airbags, and general integrity and strength of the car's structure, and its ability to withstand the impact and protect its passengers. You want a car with as many passive safety features as possible.
  • Active safety features: Active safety features are the ones that help you to avoid the accident and reduce the risk of one happening in the first place. These include ABS, stability control, and driver-assistance features such as blind-spot monitoring, adaptive cruise control, autonomous braking, and rear cross-traffic alert. We discuss the differences between active and passive safety features here.
  • Crash ratings: The presence of passive safety features is not sufficient. You also want to know how well they perform in a crash and that's why the NHTSA and IIHS crash-test cars. A car that has achieved four or five stars overall in the NHTSA's tests and that has achieved a score of "Good" in the IIHS' test criteria is considered safe. Read all about how these crash tests and safety ratings work here.
  • Size: With similar passive safety features in both vehicles, a heavier vehicle will still fare better in a crash with a lighter vehicle. Especially in America, where very large trucks and SUVs are commonplace, a small car can count against you in terms of safety when crashing into a big and/or heavy car. Even though they might fare well in crash tests against static barriers, small cars are still less safe on roads shared with big cars.
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The Safest Cars in America

The safest cars combine technology such as crumple zones with active driver assists for top scores and ratings from the authorities. The IIHS' Top Safety Pick and Top Safety Pick+ awards are an easy way to see at a glance which are the safest new cars on sale in the US, as are the NHTSA's five-star cars. The top performers include small and luxury cars, SUVs, and even new electric car producers such as Tesla.

Here is a list of the best of the best - 2021's IIHS Top Safety Pick+ winners:

  • Acura TLX, MDX, and RDX
  • Audi A6, A6 allroad, A7, Q5, and e-tron
  • Cadillac XT6
  • Ford Bronco Sport and Explorer
  • Genesis G70, G80, G90, and GV80
  • Honda Accord, Insight, and Odyssey
  • Hyundai Tucson, Nexo, and Palisade
  • Kia K5 and Stinger
  • Lexus ES, IS, and NX
  • Mazda 3 hatchback, 3 sedan, 6, CX-3, CX-30, CX-5, and CX-9
  • Mercedes-Benz C-Class, E-Class, and GLE-Class
  • Nissan Altima, Maxima, Rogue, and Murano
  • Subaru Crosstrek, Legacy, Outback, Forester, and Ascent
  • Tesla Model 3
  • Toyota Camry, Highlander, and Sienna
  • Volvo S60, V60, S90, V90, XC40, XC60, and XC90
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Conclusion

The crumple zones on cars have been improved over the years to provide us with much-needed cushioning and redistribution of potentially harmful forces in a crash, and they have been supplemented by airbags and countless other passive and active safety features to save lives. Today's cars are safer than ever, and cars of the future will likely be even safer. Buyers should research a car's safety score before buying, especially when it comes to older, used cars.

FAQs

What are crumple zones and what are they good for?

These are sections of your car - one up front, one in the rear, and one on either side - that are designed to crumple rather than hold their shape in the event of a crash. This allows them to absorb and dissipate the kinetic energy of the collision so that deceleration is not entirely instantaneous, and the occupants don't feel it quite so acutely. As a safety feature, it is one of the most important aspects of any car.

What are moderate overlap crash tests and why are they done?

The definition of the IIHS' moderate overlap test is a test in which a car does not strike a full-width barrier, but one that overlaps with only 40 percent of the car's crumple zone. This is because this is the most common type of crash, where drivers strike objects only partially with a corner of their vehicle's crumple zones as they swerve to try to avoid the obstacle.

Why did the IIHS start to perform small overlap crash tests?

The IIHS' statistics had shown that cars' outer edges are often struck in accidents, but that the front crumple zones offer little protection in such scenarios. With an overlap of only ten percent, most crash forces in this test act directly on the front wheel, suspension, cabin safety cell, and firewall. A car that performs well in a 40% moderate overlap test could still perform poorly in a 10% small overlap test. Because this is a common type of accident, the IIHS incorporated this test into its test regime in 2012. The test is performed at a speed of 40 mph.

Which was the first car ever to use purposely designed safety crumple zones?

One of Mercedes-Benz's engineers, Béla Barényi, patented the first crumple zone design in 1937 and the first production car it was incorporated in was the 1959 Mercedes-Benz W111 Fintail sedan, according to the German Patent and Trademark Office.

How do side crumple zones protect passengers?

Cars' doors and sides are very thin compared to the front and rear crumple zones, so manufacturers use very strong steel for constructing parts such as the side sills, B-pillars, and side-impact protection beams located in the doors. Additionally, a car's structure is designed to bend and distribute impact forces from the side. Finally, side-impact and curtain airbags help cushion the occupants from the blow.

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