High-speed car accidents tend to cause more severe injuries than low-speed ones. In a two-vehicle collision, the gravitational force exerted on vehicle occupants is the speed of both vehicles combined. If you were traveling at 60 miles per hour and the person who hit you was traveling at 70, for example, the total speed at which your collision occurred would be 130 miles per hour. The higher the speed of your accident, the more likely you will suffer injuries that take longer to heal.