桥梁是铁路上的主要建筑物之一。桥梁跨度的标准化不仅能节约大量的设计、制造、架设力量,而且也间接地反映了一个国家的桥梁技术水平。这个问题政策性较强,牵涉面也较广。它不仅要考虑过去的历史状况,还要考虑到今后的发展;它不仅要考虑平时的正常情况,还要考虑万一发生战争而需修复的情况;它不仅要考虑铁路本身的立交问题,还要考虑与公路、人工运河的立交问题;它不仅要考虑通航问 The bridge is one of the main buildings on the railway. The standardization of bridge span can not only save a lot of design, manufacture, erection of power, but also indirectly reflects the technical level of a country’s bridges. This issue is more policy-oriented and involves more people. It must consider not only past historical conditions but also future developments; it should not only consider normal conditions of normalcy but also consider situations to be repaired in the event of a war; it should not only consider the issue of the interchange of the railway itself, but also It is necessary to consider the problem of interchanges with highways and artificial canals; it should not only consider navigational questions