Evaluation of social costs
Problems of method
If policy decisions are to be coherent, it is essential to translate the effects of transport activities on
the environment into money terms. However, the precise way this is done would depend upon the type of
decisions to be taken. Thus, for decisions on pricing, one is generally interested in marginal costs, while for
decisions about investment, one will generally seek to assess the difference in costs "with and without" the
investment1
.
The evaluations of social cost that we are interested in here, and that may exist at either the city,
region or country level, correspond to strategic decisions that determine the main lines of policy, and are
comparable with national accounts data. This concept can be expanded using the orientations given below
(Quinet, 1991), based upon the conventional approach which consists (for an environmental parameter) of
measuring the willingness to pay and the cost of reducing the harmful effects (see Figure 2.1).