Comparative study of geometric design regulations of Railways based on standard optimization

In most developed countries globally, railway lines are designed based on four factors: speed,structure, load, and fleet type and accordingly, various regulations and standards are published to achieve a comprehensive and complete design. The basis of these four factors has been formulated. Regulations and instructions in the world based on the progress of science and technology in the design of railway lines in short periods are reviewed or developed by scientific committees to meet the needs related to the creation of railway lines. This article introduces important parameters in rail line geometry and studies the literature subject; Geometric design regulations in Iran, Sweden, Germany, CEN and TSI laws introduction have been reviewed. The reason for choosing these countries was the similarity of the fleet used, and therefore the study of the rolling stock does not fit into this topic. By comparing these regulations, the tendency to neglect the implementation of geometric parameters in new lines can be inferred except Iran. In Iran regulations do not include trains with new technologies, to the extent that there is no mention of tilting trains in Iranian regulations so that the geometric designs are stricter. In contrast, in other regulations a separate part has been defined for trains with the new technologies such as tilting trains. Finally, to optimize the criteria, the objective function must first be determined. This means that which requirements are the goal to optimize. Dimensional optimization can be done to increase travel comfort or reduce costs, or to minimize duration and cost of construction, repair, and maintenance, the optimization process can be done. According to available studies, determining a parameter as the only useful parameter or weighting the criteria is incorrect. It is only by combining the parameters that significant changes can happen.