The authors investigate whether there is a level of road tolls which will support a road system with optimum characteristics. The chapter begins with a formal development of the class of stochastic user-equilibrium models to be employed. This is followed by an analysis of the conditions under which general target link-flow vectors can be supported as stochastic user-equilibria. In particular a full positivity condition on target vectors is established under which such toll supports always exist. Additional conditions are then established under which such toll supports can be guaranteed to be non-negative. In particular it is shown that under mild regulatory conditions on link costs, such non-negative toll supports always exist for fully positive system optimum link-flow patterns. Finally a number of behavioural implications and limitations of these results are discussed.
Abstract