While safety belts restrain back-seat passengers, they're susceptible to head and neck injuries, and in many of the SUVs, the belts are relatively low tech and simply tighten up in a crash.Newer belts have sensors that determine a crash is imminent and they pull a passenger into the proper seating position before a crash, slowing the passenger's speed with the vehicle, Harkey said.Small SUVs fare poorly in new, tougher side-impact crash testThe institute used a crash dummy that represents a small woman or a 12-year-old child to test for injuries to rear-seat passengers, and Harkey says the dummy does a good job of showing risk to passengers of all sizes.Automakers responded with stronger structures and air bags to make front-seat riders safer, and all 15 small SUV models used to get good ratings.Some of the SUVs tested have more sophisticated rear safety belts, but the timing has to be worked out to function better in the milliseconds before and after a crash, Harkey said."