School bus travel is one of the safest forms of transportation, yet each year an average of nine school bus occupants are fatally injured in school bus crashes. Although much has been done to improve the safety of school buses over the years, more research may reflect new ways to better protect school bus occupants. Current school bus occupant protection is based on a concept called compartmentalization, meaning that the seats are closely spaced together, high backed, well padded, and are designed to absorb energy during a crash. Although this design works well in frontal impacts, compartmentalization may not protect occupants as well in side impacts and rollovers. The purpose of this paper is to describe the large school bus crash simulations performed by the National Transportation Safety Board and the National Highway Traffic Safety Administration in an effort to address safety issues concerning occupant protection in non-frontal collisions and also to compile accurate crash data to evaluate future occupant crash protection systems. (A) For the covering abstract see ITRD E106540.