C. An Account of a Road Network Design Method: Expressway Spacing, System Configuration and Economic Evaluation

In the decade following the worldwide economic depression of the 1930s and the ensuing world war, prosperity returned to America; in contrast, in Germany and emainder of Europe, as well as much of Asia, the struggle for survival occupied many people. Postwar prosperity in America provided sufficient income for many urban families to pursue their dreams of home ownership, often to shelter expanding families resulting from the postwar " baby boom. " Acquiring their first new car in many years, or possibly their first car ever, was also a priority for such households. Housing construction in suburban areas adjacent to large central cities, together with generous terms on mortgages for war veterans and middle income households, provided new opportunities to purchase single-family homes. The suburban location of such housing, as well as new employment opportunities on the edges of cities, made commuting by car increasingly necessary. Although these trends began only in 1945, the future shape, form and extent of American cities were changing rapidly, trends that would continue for the next 25 years until metropolitan expansion slowed in the 1970s. Before and during the war, exploratory studies were initiated to determine the scope and extent of an American system of interregional, limited-access highways. Following his inauguration as President in 1953, Dwight Eisenhower set in motion further studies leading to the authorization and design of the National System of Interstate and Defense Highways to link 90% of American cities with populations of 50,000 or more with 41,000 miles of freeways at an initially estimated cost of $25 billion; see Weiner (1997, p. 31). Envisaged and promoted as an interregional system, Eisenhower was reportedly opposed to building highways through congested cities, but the agreed-upon system did include urban radials and beltways that promised entirely new freedom of movement to urban dwellers; cf. The new field of urban transportation planning was confronted with these and related challenges as it emerged in the early 1950s. Origin-destination surveys