Abstract
Optimality is concerned with the efficient use of transport resources in terms of maximising output for a given set of inputs and economic efficiency. The concepts discussed in this chapter include: optimal networks (from the point of view of users and providers); the relationships between the transport sectors and the overall efficiency of the economy; the labour market (including the efficiency of cities and the trade-off between rents and transport costs); the role of transport in the general equilibrium view of the economy; and some implications for the appraisal and evaluation of transport investments (including the use of computer models).