Travel time savings are the main source of benefits in transport project evaluation. In its simplest form, the value of these savings have two components: the value of alternative activities after a travel time reduction, and the direct value of the reduction itself. Under fairly general conditions, the first component can be shown to be equal across alternative activities that are not constrained and yield either utility, money, or both. This is sometimes called the resource value of time and, under DeSerpa's set of definitions, it is also the value of leisure activities, usually related at equilibrium with the wage rate plus the value of work (a paid activity). In this paper it is shown that the usual association between the value of leisure and the money actually earned is not necessarily justified. A general consumer behaviour framework is proposed and used to prove this assertion. It includes all activities (leisure, work and travel). It is shown that the most interesting case is that of individuals who do not perform extra work. An interpretation of the results is made in terms of variables that are not usually observed but that could be captured using stated preferences, namely the relevant wage rate.
Abstract