According to the MO Highway Patrol, "An unbelted occupant of a 30 mph car crash hits the windshield or other interior surfaces with the same impact as a fall from a three-story building." Also, "[t]he effectiveness of an air bag system drops 40 percent when a seat belt is not used."
Missouri Highway Patrol "Rollover Simulator & Convincer: https://bit.ly/2GnxuEK
Who must wear a seat belt? Everyone in the front seat regardless of age, anyone under the age of 16 regardless of whether they are in the front seat or back, and anyone under the age of 18 that is driving or riding in a truck.
Five injured, including teens, in rollover crash at 79th and Oldham: https://bit.ly/2JZrPFC