[[abstract]]A backward safety analysis model that can deal with dangerous status by virtue of fuzzy theory is proposed in this paper. Fuzzy Petri Nets (FPN) is developed and applied to the safety analysis for three types of level crossing surveillance systems of Taiwan Railway Administration. The numerical results of proposed FPN models are fairly plausible.[[conferencetype]]國際[[conferencedate]]20081219~20081221[[conferencelocation]]Taipei, Taiwa