铁路的一个基本特点是钢制车轮在钢制轨道上运转。这时铁道车辆的运行阻力以每单位重量的阻力计,可以比其它交通工具为低。例如比汽车的橡胶轮在硬面公路上约低六、七倍,同船舶、管道不相上下,比飞机 A basic feature of the railway is that the steel wheels run on steel tracks. At this time, the running resistance of railway vehicles can be lower than that of other modes of transport in terms of the resistance per unit weight. For example, rubber tires than cars on the hard surface highway about six or seven times lower, with the same ship, pipe, comparable to the aircraft