Author(s)

F. Filippi & N. Papola

Abstract

A critical examination of the results of Mogridge and Williams clarifies some theoretical aspects of the Downs-Thomson paradox and the possibilities that road investment can worsen traffic conditions. The importance that these or similar cases with little or no effect have in practice is investigated with the data contained in Newman and Kenworthy's source book. An interesting result is that the short-term effect on average speed of new road investment in medium- to high-density areas are modest, but can produce quite considerable increases in energy consumption. The empirical analysis also shows the inadequacy of the theoretical framework for long-term effects. 1 Introduction The rapid motorisation that began in the 1950s was followed in the 1960s by a series of studies

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