Abstract: On March 12, 1991, Employee #1, a machine operator, was riding on the step platform of a tripper machine without fall protection. The tripper machine ran along a conveyor machine, dropping fertilizer into storage bins. While he was riding the tripper machine, it sped up and began to vibrate. Employee #1 panicked and tried to jump off the machine and grab a section of the catwalk railing, but fell approximately 40 ft between the machine and the catwalk to concrete ground. He was hospitalized. He had operated this machine on other occasions and had been instructed by his foreman to ride the machine from the step platform.