The public and engineers alike have become accustomed to the use of a factor of safety to
prevent failures. Unfortunately, such factors do not prevent catastrophic failures because of
rare or unusual events or circumstances. Such failures could be caused by large floods,
earthquakes, poor workmanship, inferior materials, errant sea vessels or insufficient
knowledge on which to make design judgments. This paper presents a philosophy, and
briefly describes methods, for reducing the risk of catastrophic bridge failures./Author/