Minimum decision criteria regarding the decision to make significant changes in the railway safety management system have been determined. The “Notification on Decision Criteria for Significant Changes in the Railway Safety Management System” prepared by the Ministry of Transport and Infrastructure has been published in the Official Gazette and entered into force. According to the notification, changes planned in the railway infrastructure, vehicles, operations, organizational structures of operators, and managerial practices that may affect railway safety are defined as significant changes. Developments such as transitioning from freight transportation to hazardous freight transportation or passenger transportation for railway train operators, or transitioning from conventional train operation to high-speed train operation, are listed among operational significant changes. Changing the type or modifying a railway vehicle and extending inspection and maintenance intervals in current maintenance plans are also considered within this scope. The processes specified in the “Common Safety Method and Guide for Risk Assessment” will be implemented for planning, implementing, and managing significant changes. The General Directorate of Transport Services Regulation is authorized to oversee all conformity assessment activities to be carried out in accordance with the notification. The notification covers the activities of railway infrastructure and train operators as well as maintenance responsible organizations.