Naturally, analysis by the academic literature has burgeoned along with the rapid integration of the global world economy. But, while the connection between transport and trade flows is clear, the literature often looks at these two issues (international trade and transport) separately. International trade theory often models trade frictions between countries as general costs that lump transport costs with other trade frictions, such as communication costs, regulatory costs, and even border taxes. In empirical work by international trade economists, distance between countries often proxies for transport costs, but could also be proxying for a whole host of these other trade frictions. At the same time, the transport literature rarely worries about whether the goods being transported are crossing international borders and whether this raises interesting issues for the transport sector that would not be faced for domestic transport.

自然而然，随着全球经济一体化进程的加快，学术文献中的分析也随之兴起。但是，虽然运输和贸易流动之间的联系是明确的，但文献往往分别研究这两个问题（国际贸易和运输）。国际贸易理论通常将国与国之间的贸易摩擦建模为一般成本，将运输成本与其他贸易摩擦（如通信成本、监管成本甚至边境税）相结合。在国际贸易经济学家的实证研究中，国与国之间的距离往往代表着运输成本，但也可能是其他贸易摩擦的推动者。同时，运输文献很少担心正在运输的货物是否跨越国际边界，以及这是否会给运输部门带来国内运输不会面临的有趣问题。