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Why Auto Bumpers Aren't Great In Crashes

Many automobile bumpers aren't that great, we found out in a series of crash tests released yesterday. Even minor, low-speed impacts can create damage that costs thousands of dollars to fix.

One reason for this phenomenon is that the U.S. government has lowered its standards for bumper impacts, even as cars have become more compact, more sophisticated, and more expensive to repair. The result: Americans who get into minor fender benders end up spending far more than they may expect.

The Insurance Institute for Highway Safety, a non-profit group founded by auto insurers, is trying to change this by conducting crash tests and publicizing the results on its Web site.

It's also asked the federal government to rethink its regulations. "The government standard for bumpers is very weak," IIHS' Russ Rader told in an interview on Friday. "It used to be a lot tougher. The government used to require a 5 MPH impact test, but in the 1980s that was rolled back to 2.5 MPH. The Canadian government recently weakened their standard to match ours. Now manufacturers have absolutely no incentive to build better bumpers."

In addition, the National Highway Traffic Safety Administration regulates the height and impact abilities of bumpers only for passenger cars -- not for light trucks, minivans or SUVs. It says that because some trucks are used for off-road purposes, and because others back up to loading docks, regulating bumper heights would be too problematic.

The IIHS conducts a full width bumper test at 6 MPH, and a corner impact test at 3 MPH. Some of the worst (that is, most expensive to fix) vehicles: a Toyota Prius, a Volkswagen Rabbit, a Pontiac G6, and an Infiniti G37. Cheaper cars often meant cheaper fixes, with the Ford Focus, Scion xB, and Mazda 6 doing the best in their respective classes.

"We're hoping manufacturers will compete to get better ratings in this test," Rader said. "We're already seeing some evidence they're doing this." He offered the Mazda 6 as an example; after it performed poorly on previous IIHS bumper-tests, Mazda redesigned the bumper.

For its part, the NHTSA says that the change in bumper standards from 5 MPH to 2.5 MPH was justified because it was a net benefit to consumers. It says the additional cost of repairs was offset by the reduction in the initial cost of the bumper (and presumably the money saved on gas while driving a lighter car).

Another factor is that newer cars are less likely to have extra space under the hood, so if a collision pushes the metal bar that's part of the bumper back a few inches, it hits components instead of empty space. Mark Boudreau, who runs an Arlington, Virginia collision repair shop, tells CBS News that "there's less distance between the edge of that bumper and where these very expensive components reside."

There's also the dizzying variety of vehicles that share the road, from dump trucks and an occasional farm tractor to a low-slung Corvette or Lotus Elise.

If all vehicle bumpers were all the same height, and all impacts took place with the entire bumper distributing and absorbing the force of the collision, then this would be a relatively easy problem for automotive engineers to solve.

But that's not the case: trucks and SUVs tend to be larger than cars and have bigger wheels, which means that their bumpers are higher. In a collision, a truck bumper may miss the car's bumper and instead hit the grille, hood, radiator, headlights, and even perhaps air conditioning systems. What the industry calls "bumper mismatch" means expensive repairs.

The IIHS crash tests don't involve an impact against, say, a cement wall. Rather, they involve a horizontal metal bar designed to simulate a bumper that's raised a little higher than normal car bumpers. (It's worth noting here that these particular tests measure repair costs, not passenger safety.)

"The crash that occurs mimics two scenarios: one is a scenario where you hit a vehicle whose bumper is higher, but also the kind of scenario that happens in commuter traffic, where the driver in front of you suddenly slams on his breaks," Rader said. "You slam on your brakes, and your front end is going to dive."

One way to make cars more crash-worthy is to extend the actual metal bar that sits under the vehicle's plastic fender. If it's made bigger, taller, and wider, it can cover the corner of the vehicle and protect expensive components like headlights.

Then again, bigger/taller/wider also means heavier, and manufacturers are now facing higher fuel efficiency standards. The latest government regulations require an average fuel efficiency of 35.5 miles per gallon, which means an increase of more than 8 miles per gallon per vehicle.

All else being equal, the goals of fuel efficiency and safety are in opposition; if the government relaxed the MPG rules, manufacturers would find it easier to add more metal to the front and back of cars. (Side note: I once stayed with an astrophysics professor at a Colorado university. He drove the largest pickup truck he could find based on the reasoning that additional mass provides additional safety.)

For its part, the National Highway Traffic Safety Administration says it's aware of the bumper mismatch problem and is looking into it.

"Bumper elevation is not solely responsible for mismatched contact in vehicle collisions," NHTSA says. "The effect of braking and interaction of suspension dynamics and vehicle weight can also be attributed to the mismatch. This issue is being addressed as a part of the agency's consideration of the broader issue of vehicle compatibility. Compatibility involves differences in vehicle characteristics between passenger cars and (light trucks) such as weight, height off the ground, geometry and stiffness."

There's unlikely to be any immediate solution to the problem. An earlier IIHS report raised the same issues about bumper incompatibility and repair expenses, singling out Volvos for high praise.

The year? 1973.

Declan McCullagh is a correspondent for He can be reached at
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