The accident was investigated by the National Transportation Safety Board and attributed to the failure of a compressor drive belt supplying air to the brakes on the aging vehicle and inexperience and negligence on the part of the bus driver. Various aspects of the ramp itself, including the severe radius of the curvature of the ramp and lack of warning signs, were also cited as contributing factors. The NTSB also noted that the accident was at that time the worst school bus crash and the worst highway disaster since the agency was created in 1967.^[3]

• http://en.wikipedia.org/wiki/Yuba City bus disaster