Abstract :
Transportation-related activities represent approximately 20 percent of the gross national product of the United States. The urban sprawl characterizing the recent development of our cities has resulted largely from the development of a highly efficient highway transportation system. Rail systems have been developed to a high degree and, recently, new attention has been directed to this mode. Air transport has evolved from a struggling fledgling to a major industry. Nonetheless, highway, rail, and air transportation are all facing difficult problems. Some of the major areas of activity relating to each of these modes are reviewed in this paper.
