Once again, Volvo has proven itself as a leader in occupant protection with an impressive four IIHS Top Safety Picks. Congratulations to the Volvo S80, C30, XC60, and XC90.
To determine crashworthiness - how well a vehicle protects its occupants in a crash - the Institute rates vehicles as good, acceptable, marginal, or poor based on performance in high-speed front and side crash tests, a rollover test, plus evaluations of seat/head restraints for protection against neck injuries in rear impacts. To earn Top Safety Pick for 2010 a vehicle must have good ratings in all four Institute tests and offer electronic stability control.
A new requirement for strong roofs winnows the list of Top Safety Pick winners from a record 94 in 2009. The addition of this criterion recognizes manufacturers with vehicles that provide good protection in rollovers, which annually kills more than 9,000 people in passenger vehicle. The first rollover ratings were released in March. Vehicles rated good have roofs more than twice as strong as the federal standards require. The Institute estimates such roofs reduce the risk of serious and fatal injury in single-vehicle rollovers by about 50 percent compared with roofs meeting the minimum requirement.
Not a single model from the world's biggest automaker by sales is represented among this year's winners. Toyota and its Lexus and Scion subsidiaries had a strong showing in 2009 with 11 winners but were shut out in 2010. Four other manufacturers whose vehicles have earned Top Safety Picks in the past didn't have a qualifying vehicle for 2010: BMW, Mazda, Mitsubishi, and Saab. The Honda Accord picked up the award the past two years, but the 2010 didn't earn the required roof strength rating to qualify. The Ford Fusion is another mid-size car that dropped off the list for the same reason.
How vehicles are evaluated
The Institute's frontal crashworthiness evaluations are based on results of 40 mph frontal offset crash tests. Each vehicle's overall evaluation is based on measurements of intrusion into the occupant compartment, injury measures recorded on a Hybrid III dummy in the driver seat, and analysis of slow-motion film to assess how well the restraint system controlled dummy movement during the test.
Side evaluations are based on performance in a crash test in which the side of a vehicle is struck by a barrier moving at 31 mph. The barrier represents the front end of a pickup or SUV. Ratings reflect injury measures recorded on two instrumented SID-IIs dummies representing a fifth-percentile woman, assessment of head protection countermeasures, and the vehicle's structural performance during the impact.
Rear crash protection is rated according to a two-step procedure. Starting points for the ratings are measurements of head restraint geometry - the height of a restraint and its horizontal distance behind the back of the head of an average-size man. Seat/head restraints with good or acceptable geometry are tested dynamically using a dummy that measures forces on the neck. This test simulates a collision in which a stationary vehicle is struck in the rear at 20 mph. Seats without good or acceptable geometry are rated poor overall because they can't be positioned to protect many people.
In the roof strength test, a metal plate is pushed against one side of a roof at a constant speed. To earn a good rating for rollover protection, the roof must withstand a force four times the vehicle's weight before reaching five inches of crush. This is called a strength-to-weight ratio. For an acceptable rating, the minimum required strength-to-weight ratio is 3.25. A marginal rating value is 2.5, and any lower ratings are categorized as poor.
