从50年代开始,为了与公路运输业激烈竞争,重载运输在北美铁路迅速地发展起来了。车辆制造技术和材料性能的提高,采用冷却硬化技术消除钢轨在生产过程中产生的缺陷,使轴重的增加在车辆和钢轨两个方面得到了保证。60年代初,26t轴重货车的使用数量已是相当可观了。 Since the 1950s, in order to compete fiercely with the road transport industry, heavy-haul transport has rapidly developed in North American railroads. Vehicle manufacturing technology and material performance improvement, the use of cooling hardening technology to eliminate rail defects in the production process, so that the increase in axle load in both the vehicle and the rail has been guaranteed. In the early 1960s, the number of 26t axle trucks was already considerable.