驮背运输(piggyback),也叫做拖车装于平车之上运输(trailer-on-flatcar,简称为TOFC),它是美国铁路货运的一个重要方面。近年来,在制成品和半成品的运输方面,铁路在与公路的竞争中丧失了不少运量。然而在此期间,驮背运输却有了巨大的发展。这种形式的陆路联运传统上是长途的,其中最兴旺的是从芝加哥到纽约和洛杉机的驮背运输,其运距分别为1500和3500公里。 Piggyback, also known as trailer-on-flatcar (TOFC), is an important aspect of U.S. railroad freight. In recent years, the railway has lost a lot of traffic in the competition with the highways in the transportation of manufactured goods and semi-finished products. However, during this period, there has been a tremendous development in pack transport. This form of land transport is traditionally long-haul, with the most prosperous being the carry-on transport from Chicago to New York and Los Angeles at distances of 1,500 and 3,500 km respectively.