The 2009 Ford Flex has earned five-star frontal and side-impact crashworthiness ratings in the latest round of vehicle crash-safety tests conducted by America’s National Highway Traffic Safety Administration (NHTSA). The Flex only scored a four-star rating, however, for both FWD and AWD versions in the agency’s rollover tests.

Key to the Flex’s prowess in the tests is its full array of standard safety equipment. This includes dual front air bags, headliner mounted side curtain air bags, four-wheel anti-lock brakes, electronic stability control and a tire pressure monitoring system.

The Flex also benefits from a novel construction method, which features lightweight aluminum-coated boron steel in its body structure. The design also includes high-tensile steel in the B-pillars and the addition of specially-designed side intrusion beams.

The NHTSA's frontal collision ratings are determined by placing crash-test dummies in the driver's seat and front-passenger seat and securing them with the vehicle's safety belts. Vehicles are then crashed into a fixed barrier at 35mph, which is equivalent to a head-on collision between two similar vehicles that are moving at 35mph. The five-star rating indicates a 10% or less chance of serious injury to a belted occupant in the front seat.

Side-impact crash testing represents an intersection-type collision with a 1,368kg barrier moving at 38.5mph. In this case, a five-star rating indicates a 5% or less chance of serious injury.