Hand Book of transportation Engineering

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Transportation systems of regional and national extent are composed of networks of inter-
connected facilities and services. It follows that nearly all transportation projects must be

analyzed with due consideration for their position within a modal or intermodal network,

and for their impacts on network performance. That is, the network context of a transpor-
tation project is usually very important. Thus, it is appropriate to begin a volume on trans-
portation engineering with a chapter on national transportation networks.

The subject of national transportation networks may be approached from at least two

different perspectives. One approach, common to most introductory transportation textbooks,

describes the physical elements of the various transport modes and their classification into

functional subsystems. A second approach focuses on the availability of national transpor-
tation network databases and their use for engineering planning and operations studies. The

latter approach is emphasized in this chapter, with the aim of providing the reader with some

guidance on obtaining and using such networks. In describing these network databases,