本世纪以来,公路运输得到了迅速发展。目前世界运输网的总长度约为3000万公里(不包括海运路线),其中公路约占2000万公里。第二次世界大战以后,随着科学技术和经济的发展,各国普遍重视以高速公路为主的公路网建设,并投人大量财力和物力。一些发达国家已基本建成了较完整的高速公路网,大大改善了运输条件,提高了经济效益。一些发展 Since the beginning of this century, road transport has been rapidly developed. At present, the total length of the world transport network is about 30 million kilometers (excluding maritime routes), of which about 20 million kilometers are highways. After the Second World War, with the development of science, technology and economy, all countries generally attach importance to the construction of the expressway-based road network and invest a great deal of financial and material resources. Some developed countries have basically completed a relatively complete highway network, which has greatly improved transport conditions and raised economic benefits. Some development