Data on all trips from two studies are analysed to show that, as household income increases, the money spent per mile travelled increases, but the time spent per mile decreases. The use of generalized time gives a different picture of the relationship between income and the total time and money spent on travel to that given by the use of generalized cost. The choice between using generalized time and generalized cost in evaluation is fundamentally a choice between assuming that the marginal utility of time and that of money is constant. The procedures at present recommended by the Department of the Environment in U.K. have elements of both assumptions, with some loss of consistency. There are some a priori reasons for expecting constant marginal utility of time to be a more plausible assumption than constant marginal utility of money. Time is, by its nature, equitably and unalterably distributed, not subject to the accidents of inheritance, theft, chance, inflation, social system or government decree. Everybody starts of with 24 hours a day. Although the amount of "free" time varies, of course, it probably varies within a much smaller range than the amount of wealth, certainly for the employed population. In allocating time between various activities, the use of words like spend, save, waste, lose, gain, and so on is a reflection of how deeply rooted in language and thought is the concept of time as a fundamental currency. This approach is strengthened by recent developments in two areas where generalized cost has been found to be a useful tool of analysis: (a) in explaining and predicting the behavior of travellers, and (b) in evaluating the social costs and benefits arising from transport projects. Only non-working time will be considered here. It is suggested that in some circumstances generalized time would allow behaviourally correct relationships between non-working time and money to be used in evaluation.

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    Radarweg 29
    Amsterdam,   Netherlands  1043 NX
  • Authors:
    • Goodwin, P B
  • Publication Date: 1974-4

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 1-21
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00072547
  • Record Type: Publication
  • Source Agency: TRANSPORTATION
  • Files: TRIS
  • Created Date: Dec 31 1976 12:00AM