抄録
Accidents at level crossings have big social impact. Therefore it’s very important to prevent them. Existing level crossing system safety is controlled by logic configured with traditional electrical relays and it has a history of high level of safety and reliability over several decades. Control logic implemented by means of such legacy mechanism includes deep tacit knowledge. Therefore, clarifying the implicit design philosophy is required. By conducting FRAM analysis for level crossing implementations, we have found out hidden design secrets and beautiful “pyramid” architecture in highly complex relay-based logic. In this paper, success and risk cause of this legacy system will be shown.
