ARLINGTON, Va. — Among seven midsize inexpensive four-door cars recently subjected to 40 mph frontal offset crash tests, only one earns a good overall evaluation for crashworthiness. The top-performing Subaru Legacy, a 2000 model, also earns a "best pick" designation from the Insurance Institute for Highway Safety, which conducted the tests. In contrast, the 1999 Daewoo Leganza turned in the worst crash test performance, earning an overall evaluation of poor.
The Pontiac Grand Am/Oldsmobile Alero also is rated poor. The Nissan Altima is marginal, and the other midsize inexpensive cars the Institute recently evaluated — Mazda 626, Saturn L Series, and Chevrolet Malibu — are acceptable. This brings to 14 the number of designs of midsize inexpensive cars the Institute has rated. Five earlier designs of the same models also have been evaluated.
Subaru Legacy: best performer in group
Daewoo Leganza: worst performer in group
The contrast in crash test performance between the Legacy and the Leganza "was dramatic," says Institute president Brian O'Neill. "The occupant compartment, or safety cage, of the Legacy held together extremely well, and most injury measures recorded on the crash test dummy were low. But in the Leganza, the occupant compartment suffered a major collapse, and there were some high injury measures. Plus the dummy in the Leganza's driver seat flailed around out of control during the offset crash test. The steering column also moved excessively."
The Institute's crashworthiness ratings — good, acceptable, marginal, or poor — are based primarily on performance in the 40 mph frontal offset crash test into a deformable barrier. This impact is especially demanding of vehicle structure. The driver side of the vehicle hits the barrier, so a relatively small area of the front-end structure must manage the crash energy. This means intrusion into the occupant compartment is more likely to occur than in a full-width test.
Structural performance is key
The dramatic differences in the structural performances of the Legacy and Leganza are apparent in the measurements of intrusion into the occupant compartment recorded by Institute researchers after the offset test. "Lower intrusion measurements indicate a vehicle's safety cage and crumple zone are doing their jobs," O'Neill says, and every measurement was much lower in the Legacy than the Leganza:
Measures of occupant compartment intrusion, 40 mph frontal offset crash test
| ||A-pillar movement rearward (cm)||Footwell intrusion||Brake pedal intrusion (cm)||Instrument panel rear movement|
|left (cm)||center (cm)||right (cm)||footrest (cm)||left (cm)||right (cm)|
|2000 Subaru Legacy||1||10||18||10||7||14||0||1|
|1999 Daewoo Leganza||10||36||37||29||31||36||15||15|
"Good structural design is the key to good performance in the offset test," O'Neill explains. "If a car's front-end structure absorbs and manages the crash energy so the occupant compartment remains largely intact with little or no intrusion, then the dummy's movement is likely to be controlled, and injury measures are likely to be low. In contrast, poor structural design means greater likelihood of poor control of the dummy and high injury measures."
O'Neill adds that "the way to protect people in serious frontal crashes is to ensure that the occupant compartment, or safety cage, remains intact. When this happens, the restraint system — the safety belts and airbags — can prevent significant injuries, even in serious crashes. But when major intrusion occurs, even the best restraint system cannot prevent all injuries. It's the same concept as shipping a fragile object — it doesn't matter how well it's protected by foam or other packaging inside a box, if the box gets seriously damaged during transit, the object inside is likely to break. Today more of the vehicles we test have good structural designs, and their occupant compartments, or safety cages, remain largely intact."
The good vehicle designs in the Institute's latest crash tests "are because more and more automakers are incorporating offset tests into the vehicle development process. The manufacturers are doing this because they know many car buyers want the best occupant crash protection they can get," O'Neill says.
Institute and government crash tests complement each other
The Institute's crashworthiness evaluations are based primarily on results from the frontal offset crash test at 40 mph. Each vehicle's overall evaluation is based on three aspects of performance — measurements of occupant compartment intrusion, injury measures from a Hybrid III dummy positioned in the driver seat, and analysis of slow-motion film to assess how well the restraint system controlled dummy movement during the impact.
The federal government has been testing new passenger vehicles in 35 mph crash tests since 1978. This New Car Assessment Program has been a major contributor to crashworthiness improvements — in particular, improved restraint systems in new passenger vehicles. The Institute's offset tests, conducted since 1995, involve 40 percent of a vehicle's front end hitting a deformable barrier at 40 mph. This test complements the federal test involving the full width of the front end hitting a rigid barrier. Both tests are contributing to improvements in crashworthiness — in particular improved crumple zones and safety cages.
The same 40 mph offset crash test is used to evaluate new cars by the European Union in cooperation with motor clubs and by an Australian consortium of state governments and motor clubs.