Minimum decision criteria have been determined for making significant changes in the railway safety management system. The “Regulation on Decision Criteria for Major Changes in Railway Safety Management System,” prepared by the Ministry of Transport and Infrastructure, was published in the Official Gazette and entered into force. According to the regulation, changes planned in the railway infrastructure, vehicles, operations, operators’ organizational structures, and managerial practices that may affect railway safety are defined as major changes falling within minimum decision criteria. Developments such as transitioning for railway train operators from freight transportation to hazardous materials transportation or passenger transportation, and from conventional train operations to high-speed train operations were listed among significant operational changes. Also included in this scope was the modification of train types or the extension of inspection and maintenance period intervals in existing maintenance plans. Processes outlined in the “Common Safety Method and Guide for Risk Assessment” will be implemented for the planning, implementation, and management of major changes. The Directorate General of Regulation for Transport Services has been authorized to oversee all compliance assessment activities conducted in line with the regulation. The regulation covers the activities of railway infrastructure and train operators, as well as maintenance responsible entities.