In 1998 my wife was also struck by a garbage truck. For her the saying "like getting hit by a Mack truck" has true meaning.
She had dropped off the youngest daughter at one school and was driving the seven or so miles to the other daughters school and her work. The truck driver was distracted by a dog and pulled out of a sideroad from the left and struck the Voyager minivan in the left side barely hitting the drivers door but totaly destroying the sliding door behind. By the skid marks it was visible that my wife's vehicle was knocked more than six feet to the right in about ten feet forward travel. She straddled a sewer, crossed another sideroad, and traveled more than sixty feet on a steep sidebank before STEERING THE VAN BACK INTO THE ROAD AND STOPPING. It she had continued on the bank as it got steeper the van would have flipped.
In other words the seatbelt held her in place behind the steering wheel and allowed her to control the vehicle to a safe stop even though she was hurt.
After the accident we talked to a retired Kentucky state police officer who said he had investigated hundreds of fatal accidents in his thirty years but could only name one in which the victims would have been better off without seat belts on.