Adapting French Cities to Car Traffi c during * the Post-war Years: Uncle Sam’s Math Lesson

6 Adapting French Cities to Car Traffi c during * the Post-war Years: Uncle Sam’s Math Lesson

In the aftermath of WorId War II, America greatly contributed to the economic reconstruction and development of Europe. Thanks to the Marshall Plan, Europe was able to rebuild much of what had been destroyed during the war. However, the transfers from America to Europe were not only economic and technological. Indeed, in some fi elds, in particular roadworks and car traffi

c, European engineers continued to draw inspiration from American methods, as they had been doing since long before the war.

The infl uence of American technology on European engineers concerned not only the fi elds of roadworks and regulatory road signs, but also that of traffi

c forecasting. Though forecasting traffi c fl ows between cities is not too diffi cult, within cities it becomes a complex task, requiring sophisticated techniques. Since cars were popular in America long before they became so in Europe, American engineers were already experienced in solving the problems now facing their European counterparts. The latter were thus strongly tempted to borrow American methods through a transfer of ‘intellectual technology’.

The way this happened in France is particularly interesting, since the transfer process was not taken over by consulting fi rms, as was the case in other countries, but was kept under state control. Indeed, the state was responsible for building roads and conducting the necessary surveys, and also, at the time, for urban development and city planning. Our study spans the years 1950 to 1975. After 1975, during the political and administrative decentralization process, these forecasting methods continued to be used. At the same time, public opinion was becoming increasingly aware of environmental issues, such as landscape preservation and quality of life. Today, environmental activists are blocking the construction of new urban freeways. Will the American methods transferred to France to adapt cities to car traffi

c fail because of their inability to take account of environmental issues? A study of how the situation evolved in France from 1975 till now should enable us to answer this question.

The fi rst traffi c forecasts

First and foremost, let us take a closer look at the history of traffi

c forecasting. Various counting methods were used very early on to measure traffi

c fl ows. In Europe and in America, counting urban car traffi c was considered a means to evaluate how wide roads should be built (Danger, 1935; Swan, 1922). ‘Origin-destination’ surveys were developed in the United States before World War II. Their aim was to determine where to build road bridges (to cross rivers or railroad tracks), on the basis of motorists’ itineraries (Clark & Peters, 1965). These surveys revealed ‘ desire lines’ which diff ered from actual routes. In order to forecast future traffi

c fl ows, American forecasters simply extrapolated on the basis of traffi c ‘growth factors’ such as the increase in car ownership rates (Patterson, 1966; Stopher, 1971).

* Previously published as « Adapter les villes françaises à l’automobile dans les décennies d’après-guerre : la leçon de calcul de l’oncle Sam ». In: Kaspi, A. (2000, ed.) Les relations franco-américaines dans le domaine de la technologie. Proceedings of a colloquium organised at La Fondation Singer-Polignac, 26 November 1998. Abbeville: F. Paillart. Included with permission.

Chapter 6: Adapting French Cities to Car Traffi c During the Post-war Years: Uncle Sam’s Math Lesson

In the early forties, a traffi

c forecasting method which could be applied to an entire urban area (both existing and projected) was developed in Detroit (Dutton & Starbuck, 1974). This technique was much more ambitious than the previous ones, and rather specifi c circumstances explain its invention. The automobile and road industries were pressuring the government to allocate more funds to the construction of roads, especially in urban areas. These demands were met thanks to the 1946 Federal Highway Act. However, given the nature of these funds (a special fund fi nanced by fuel taxes), the Bureau of Public Roads demanded that investments be justifi ed by strict methods. Advances in computer technology made it possible to perform calculations which so far had been impossibly diffi cult. In this context, Voorhees (1956), using both theoretical analysis and practical experience, developed a statistical-mathematical model based on a ‘general theory of traffi c movements’. Thanks to this model, he was able to meet both the automobile lobby’s and the American administration’s demands by drawing up guidelines to promote investments for the construction of roads, to increase car traffi c and boost the automobile market, all this at minor cost (illustration 6.1). After Detroit, these new methods were extended to Chicago and Pittsburgh and gradually, to other cities all over the U.S.

Thanks to strong and thickly spread asphalt road surfaces, more roads can be built for less tax money

An increase in the number of roads with such surfaces

More good roads

means that the level of

means an increase

fuel consumption also

in car traffic and

increases, thus generating

increased mobility

more tax revenue

More tax revenue means more dollars can be spent on the building and maintenance of roads with new surfaces

Illustration 6.1

The magical Circle of Asphalt. ( Asphalt Insitute, 1966)