Mine transportation of materials in underground mine workings is realized by mine underground railways as well as by suspended monorails or floor-mounted railway. Transportation is realized on tracks placed on the floor of working or on rails suspended to roadway support. Each transport operation must be preceded by a transport design project, made in accordance with obligatory legislation. A part of the project are traction calculations. Their implementation in a computer program allows for minimization of the possibility of errors during the configuration of suspended queues and conducting traction calculations, which consequently leads to improve the level of safety. The article discusses the modular Safe Trans Design system, supporting the design of auxiliary mine transportation. The system has been implemented in the mines of JSW S.A. The assumptions and structure of the system as well as algorithms of operation of the ‘configurator of transportation sets’ and ‘assessment and reporting module’ are presented. The method of creating an auxiliary mine transportation system project is presented. Safe Trans Design system is used in planning, organizational and training activities implemented as part of transport safety management in mining plants. Developed methods can be easily adapted to other legislations of hard coal producers’ countries, where suspended monorails are used in underground auxiliary mining transportation systems.