|t's a long drive from the
demolition derby at the county fair to a formal crash testing facility, where the
length of the main show is measured in thousandths of a second. If you ever see a crash
test live, you'll find it hard not to say "Wow!" So much energy, so little time!
Crash testing can be a lot like fuel economy testing. Each test procedure gives a different result for the same vehicle. That makes it important to standardize tests so you can compare those done at various times and places.
|Each test procedure
gives a different result
for the same vehicle.
The industry term--crashworthiness--confuses many people. Have you said or thought, "How come it costs so much to repair my car? I was hardly moving when I bumped that pole!" That's not crashworthiness in car-speak. It's damageability.
A better word for crashworthiness might be "injureability." Human survival in a crash is injureability (or crashworthiness); car survival in a crash is damageability. People can't be replaced; cars can.
In a crash, the car is sacrificed to protect the occupants. As the car crumples, the structure absorbs energy before it reaches the occupants. If little or no crumpling occurred in a severe crash, the belts and bags would have to absorb all the crash energy. Today the entire vehicle makes up the safety system; take away one crash feature and the others have to do more--if they can.
The most commonly published crash test results are from the New Car Assessment Program (NCAP) of the National Highway Traffic Safety Administration (NHTSA), in Washington, D.C. The agency tests about 35 new vehicles every model year. NHTSA reports previously tested vehicles that remain unchanged again with the results from the new vehicles. In its tests, NHTSA rates vehicles with one to five stars--the best rating--in four areas: frontal and side crash, driver, and front passenger.
All new vehicles have to comply with crashworthiness standards at the time of manufacture. The frontal crash compliance test calls for a 30-mile-per-hour (mph) impact into a rigid, fixed barrier. That's equivalent to a head-on crash between two identical vehicles at 30 mph. The NCAP test is at 35 mph, producing an impact 36% more severe. At 38.5 mph, NCAP's side-impact test is 32% more demanding than the minimum standard 33.5 mph. NCAP has reported side crash results since 1997 when new standards became effective.
Why test beyond what the standards require? The government's safety standards are minimums, with simple pass/fail reports. Like pass/fail academic reports, they don't give information about how much above the bare minimum what was tested performed. All cars being sold pass. The more-stringent NCAP tests try to show differences between vehicles exceeding the minimum requirements.
Information about a car's tire inflation label plays a role in crash tests. Testers load cars to full cargo capacity for testing. Not all manufacturers, though, specify the same cargo capacity for vehicles of similar size and trunk volume--the difference can be as much as 200 pounds. Asian cars usually have the lightest cargo weight capacities, and the European cars the heaviest. American cars fall in the middle. A 200-pound difference on a 3,000-pound car can reduce the test's severity by 7%.
|A better word for
NCAP rating stars simplify and combine complex measurements of maximum survivable head and chest injury levels in a crash to show a relative level of protection. Five stars, the best rating, means a 10% or less chance of serious, life-threatening injury in a frontal crash of this severity. Break-points for the other stars are: four = 20%, three = 35%, two = 45%, one = anything greater than 45%.
The side-impact crash test only considers risk of serious chest injury. That changes the risks for each star rating for the side-impact test: five = 5% chance, four = 10%, three = 20%,
two = 25%, one = greater than 25%. The risks of serious injuries appear different for each star level between side and frontal crash tests, but they are in fact comparable, says Jim Hackney, director of NHTSA's Office of Crashworthiness Standards. That's because, "In our side crash tests, only one factor--chest injuries--is contributing to the risk-of-injury assessment."
Another factor to consider when evaluating test results is that frontal crashes occur twice as often as side crashes.
The NCAP tests already have improved vehicle crash performance, Hackney points out. "Very few vehicles are rated less than three stars in the frontal tests now. It wasn't that way when we began the program [in 1979]."
Crash tests are not purely American food for consumer thought. Europe, Australia, and Japan all have programs for publishing auto crash test information. You can access these from the crash testing page of NHTSA's Web site. In Germany, a major automotive magazine has its own widely respected crash testing program. While consumers will see familiar car names in these other test reports, you can't compare the results to NCAP tests. The tests these organizations do are different.
As safety systems continue to improve, so do crash tests. Now the NCAP and compliance tests use anthropomorphic test devices--car-speak for "dummies"--simulating a median-size-and-weight male. In the near future, NHTSA will be requiring additional air bag testing with a fifth-percentile female dummy, representing the smallest 5% of women.
With male and female dummies around, child dummies soon follow. On the way are dummies of a 12-month old infant and three- and six-year-old children. These dummies will help test advanced air bag systems that sense and control air bag inflation according to the size of the person in the seat. A large, heavier 95th-percentile male dummy will join the family later.
The Insurance Institute for Highway Safety (IIHS) in Arlington, Va., has been using a new partial frontal test since 1994 to supplement the NCAP results. The IIHS performs an offset-40% frontal test at 40 mph with a deformable barrier. Forty mph is the median speed for fatal crashes, according to Julie Rochman, IIHS director of communications. "Half of all fatal crashes happen below 40 mph."
This test is popular in Europe. It differs from the NCAP test in speed, some energy absorption by the barrier, and in all the impact affecting only 40% of the front width of the car.
The offset test considers the situation when two vehicles collide head-on, but without perfect alignment. Offset tests evaluate the structure of the vehicle more than the full-frontal test does. The full-frontal test is more demanding of the restraint system. "Our test complements the government's NCAP test," says IIHS' Rochman. "Each one emphasizes a different part of the crash performance of a vehicle."
Most of the impact load in an offset test is concentrated on one side of the car. Because of this, offset testing causes more deformation of the passenger compartment--highlighting problems in lower leg injury risks, not seen in the standard frontal test.
The European community favors the offset test as a sole test; NHTSA, however, sees it as an additional test to the long-standing full-frontal test. NHTSA will use the offset test with the new female dummy in testing safety compliance of advanced air bags that are required in all 2006 vehicles. Phase-in will start at least three model years before that.
NHTSA's Hackney passes on an important perspective on crash tests for consumers. "Exposure to risk is not worked in the NCAP ratings. Small cars are exposed to more risk than larger cars."
Why? Remember that the tests simulate a crash with a vehicle of equal weight. "Small cars will tend to perform worse than the tests would indicate because they are more likely to have a crash with a larger vehicle," Hackney observes. There simply are more large vehicles on the road.
will save you from
doing your own
vehicle crash test.
|Choosing your next car|
Whether from NHTSA or IIHS, crash test results add to the prepurchase information available to consumers. Only you can decide where crashworthiness falls in your buying priorities.
When shopping, remember the other half of the safety equation: crash-avoidance features. Dodging disaster will save you from doing your own vehicle crash test.
|©1998 Credit Union National Association, Inc.|