Traffic Direction Diagrams (1943)

The rise of the automobile in the 1920s disrupted the field of city planning. The 1909 Plan of Chicago had been concerned with beautifying the city in part by rationalizing railroad terminals and widening streets to relieve “vehicular traffic”—in this case, a tangle of trolley cars and horse-drawn wagons. But the internal combustion engine represented a dramatic advance in technology, allowing flexible, fast, and individualized transportation. New forms of roads to appease the automobile would be needed.

Robert Moses was among a generation of planners who sought to adapt cities and regions to the physical, social and economic changes wrought by the automobile. He dominated planning in greater New York from the 1930s to the early 1970s through his appointment as head of several semi-independent city and regional agencies tasked with everything from roads to urban renewal to hydro-electric power. Through political skill and force of personality, he created a planning empire that allowed him to plot new road networks, purchase parkland, and build infrastructure of all types, most of it funded by tolls, bond issues, and federal programs. The range of public works that bore his influence in New York is enormous, from Lincoln Center and the Triborough Bridge to a system of expressways and state parks.

These achievements attracted the attention of businesses leaders in Portland, Oregon, and in the early 1940s, when Moses’s reputation was at its height, they asked him to create a plan for what they expected to be continued growth of their city in the postwar era. A wartime spike in shipbuilding and other military industries had expanded Portland’s population and economy. Moses’s 1943 plan recommended a host of infrastructural enhancements. These ranged from sewage and water facilities to schools and parks. However, the centerpiece of the plan was the expansion of Portland’s arterial highways, including the construction of expressways much like those he had been building in New York. The most ambitious of the plan’s features was a superhighway girdling central Portland that involved the construction of two massive new bridges across the Willamette River.

Limited access highways were a relative novelty at that time, and engineers were still experimenting with their design. In this series of diagrams, the Portland Improvement Plan explains how various interchanges might channel traffic to and from surface streets and branch highways. The car would be king in Portland, as elsewhere.



Abbott, Carl. Portland: Planning, Politics, and Growth in a Twentieth-Century City. Lincoln: University of Nebraska Press, 1983.

Caro, Robert. The Power Broker: Robert Moses and the Fall of New York. New York: Knopf, 1974.

Bianco, Martha J. “Robert Moses and Lewis Mumford: Competing Paradigms of Growth in Portland, Oregon.” Planning Perspectives 16 (2001): 95-114.

Lewis, Eugene. “Robert Moses.” American National Biography, vol. 15. New York: Oxford University Press, 1999.

Nash, Gerald. The American West Transformed: The Impact of the Second World War. Bloomington: Indiana University Press, 1985.



Portland Bureau of Transportation. “Transportation History.”


“Traffic Direction Diagrams,” in Robert Moses, Portland Improvement (New York, 1943), pp. 29, 31. Ryerson and Burnham Libraries, The Art Institute of Chicago