In this paper, we provide safety requirements and advices to guarantee the safety of an interface in a level crossing system which is an interface between the conventional facilities and the new ATP (Automatic Train Protection) system, as well as we accomplish a safety management for the facilities of a country that has a different standard with already standardized ATP system. The system model has been made based on a safety activity of the international standard, and then a tolerance of a risk by the safety activity through PHA (Preliminary Hazard Analysis) has been analyzed. finally we achieved HIA (Hazard Identification and Analysis) for the assumptions that have been produced from a operating scenario and a functional interface. Thus, the safety requirements for the interface has been provided from the safety plan of HIA, and we showed the safety activity to guarantee the system safety through HIA which was depend on the design.