Book excerpt: Federal and other decision makers have had a renewed interest in how high speed rail (HSR) might fit into the national transport. system and address increasing mobility constraints on highways and at airports due to congestion. This report reviews: (1) the factors affecting the economic viability-- meaning whether total social benefits offset or justify total social costs -- of HSR projects, incl. difficulties in determining the economic viability of proposed projects; (2) the challenges in developing and financing HSR systems; and (3) the federal role in the potential development of U.S. HSR systems. The auditor interviewed fed., state, local, and private sector officials; and reviewed HSR development in France, Japan, and Spain. Charts and tables.