The idea is that if a crash occurs, the child may be thrown around within the compartment but the design of the seat compartment absorbs the crash forces and protects the child. However, the seats currently installed in school buses are different from those recommended by UCLA researchers. Seat belts are not required in school buses over 10,000 lbs. The protection exists and is in force without depending on any action by the children or any extra special supervision by drivers or monitors. Seat belts require discipline and supervision to keep them clean, unraveled, in use, and properly adjusted.
Compartmentalization works equally well for one, two or three students per seat.
Today's 39-inch wide standard seats may contain three small children or two large ones or any combination in between. Compartmentalization works whether students have fully developed abdominal areas or not. They need the help of chest harnesses also, which adds to the complexity of a proper safety belt solution. Compartmentalization, once it has done its energy absorbing job, leaves the student free to escape the bus. Seat belts could leave students strapped in, upside down, perhaps unconscious, in burning or flooding buses.