First, a simple theoretical model is developed that determines optimal prices for private and urban transport services in both the peak and off-peak periods of the day, taking into account all relevant private and external costs. Second, the model is implemented to study pricing policies in Belgium, using recent estimates of private and social marginal costs. Several applications are then considered.

Exceptional changes in bus and underground rail fares in London in the early 1980s prompted analyses of the effects of fare levels and petrol prices upon the numbers of road casualties in London. Earlier estimates of the number of extra casualties associated with a period of unusually high fares in the early 1980s are shown to have probably been too high.

In public transport systems with self-service fare collection passengers can decide whether to pay the fare or not. A passenger who does not pay is subject to a risk of being fined. The paper provides some empirical support for the hypothesis that passengers behave as expected utility maximisers.