ARLINGTON, Va. — New car designs are performing much better than their predecessors in 40 mph frontal offset crash tests. This is an important conclusion from a new round of tests by the Insurance Institute for Highway Safety involving seven car designs — two small models, one midsize inexpensive model, one large family car, two large luxury cars, and one midsize luxury car.
The offset tests are the primary basis for assigning crashworthiness ratings of good, acceptable, marginal, or poor to new cars. The best performers also earn the highest rating, a "best pick" designation.
Civic and Focus improve
A 2001 Honda Civic and 2000 model Ford Focus earn good overall ratings for crashworthiness. The Civic also earns a "best pick" designation. Both cars are improved compared with the acceptable ratings assigned to earlier designs — 1997 Civic and 1997 Ford Escort (Focus will replace Escort).
High ratings for luxury models
In 1997 the Lexus LS 400, a large luxury car, earned the highest possible crashworthiness rating, so there wasn't much room for improvement when Lexus introduced the replacement, a 2001 model LS 430. The new design matches the good overall rating and "best pick" designation earned by the 1997 model, but the LS 430's airbag and safety belt pretensioners did deploy slightly late in the offset test. This wasn't serious enough to affect the car's overall crashworthiness rating, but it did result in a downgraded restraint system evaluation from good to acceptable because the dummy's head contacted the steering wheel through the airbag during the test.
"The manufacturer didn't settle for this," Institute president Brian O'Neill points out. "Toyota was searching for perfection and wanted the highest rating in every individual category, not just a good overall evaluation, so the company made a minor change in the wiring to some of the LS 430's airbag sensors and asked for another test. In the second offset test, the airbag and pretensioners deployed earlier than in the first test. As a result, the new model earns good ratings for its restraints as well as for its structural performance and injury measures recorded on the dummy."
The Mercedes E class, another large luxury car, improves from acceptable for the 1997 model to good for the 2001 model, which also earns a "best pick" designation. The 2001 Mercedes C class, a midsize luxury car not previously tested, rates good overall and is a "best pick."
Stratus improves dramatically
A Chrysler LHS improves from poor (1999 model) to acceptable (2001 model), while another car from the same manufacturer, the redesigned Dodge Stratus, posts the biggest improvement in the Institute's latest round of 40 mph offset tests. The 2001 Stratus earns a good overall crashworthiness rating compared with a poor rating for the 1995 Chrysler Cirrus ("twin" of Stratus).
Structural design is key to good performance
The Institute's frontal offset crash test into a deformable barrier is especially demanding of vehicle structure. The driver side hits the barrier, so a relatively small area of the vehicle's 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.
"Good structural design is the key to good performance in the offset test," O'Neill notes. "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."
The crash test of the 2001 Stratus, compared with its predecessor Cirrus, provides a good example of improved structural design — that is, a design that allows less intrusion into the occupant compartment. Lower intrusion measures indicate a vehicle's safety cage is doing what it's supposed to do, and 9 of 10 intrusion measures are dramatically lower for the new Stratus design compared with the old Cirrus.
Measures of occupant compartment intrusion (cm), 40 mph frontal offset crash test
"The occupant compartment of the old Cirrus essentially collapsed, allowing far too much intrusion," O'Neill points out. "In contrast, the occupant compartment of the new Stratus held up well, with much less intrusion. As a result, the dummy's movement was controlled better, and the injury measures were generally good."
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."
1995 Chrysler Cirrus:
2001 Dodge Stratus:
far less intrusion
Institute and government crash tests complement each other
The Institute's crashworthiness evaluations are based primarily on results of 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 test.
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.