The economic interdependence of the different countries of the world explains the great importance of international transportation and, consequently, of legal rules able to make sure that the transfer of goods with the utmost simplicity, safety, and speed will be practicable. If this is true for the world as a whole it is, obviously, even truer in the case of Europe, a densely populated area, divided among many sovereign states. Up to a certain point the purely national legislation of the different countries may be able to provide for international transportation as well, but this point is soon reached and then international cooperation becomes a necessity. This works, at first, through bipartite agreements—which also serve as stop-gaps when attempts at broader collaboration have failed—but the truly promising way to regulate international transportation is by multipartite conventions. In Europe agreements of this type have existed for a long time.