In 1977, a series of Federal Motor Vehicle Safety Standards (FMVSS) for school buses became effective, mandating different performance standards for school buses compared to other buses. Because data on the crash performance of school buses built to these standards were lacking, the National Transportation Safety Board conducted a series of in-depth accident investigations from 1984 to 1988. The study sought to determine how well federal school bus standards were working to protect passengers from injury and whether changes in the standards were needed. This paper reports on the crash performance of small poststandard (manufactured after April 1, 1977) school buses and vans used for school transportation. Occupants of the small school buses generally fared well in the accidents investigated. As a result of this safety study, recommendations were issued to the National Highway Traffic Safety Administration, manufacturers of small school buses, and various associations of school-transportation officials and contractors. The recommendations include: conduct research on the design of restraining barriers; determine the feasibility of requiring lap/shoulder belts or other restraints with uppertorso support for passengers; collect data on roof and joint strength; amend federal performance standards for school bus windshield retention; develop performance standards for boarding door controls in certain small buses; and correct improper installation and use of lapbelts and other restraints. Appendices contain case summaries and indexes of cases, bus-design information, data on injuries and accidents, and a list of FMVS standards mentioned in the recommendations. (LMI)