道岔是铁路线路中的薄弱环节,其质量状态良好与否,直接关系到运输的安全。自六十年代中期以来,正线及到发线上的旧型道岔逐渐更换为TB399-64或TB399-75型道岔。实践证明,它对提高线路设备质量及保证运输安全均发挥了较大的作用。但是,随着行车密度和行车速度的提高及机车轴重的增大,特别是重轴车辆比例日益增加,处于运输繁忙干线上 Turnout is the weak link in the railway line, the quality of the state is good or not, is directly related to the transport safety. Since the mid-1960s, old transitions on the main and departure lines have been gradually replaced by TB399-64 or TB399-75. Practice has proved that it has played a greater role in improving the quality of line equipment and ensuring transport safety. However, as the driving density and traveling speed increase and the axle load of the locomotive increases, especially the proportion of heavy-axle vehicles is increasing day by day, and it is on the busy trunk line