Transport systems in many cities need actions to deal with congestion and poor air quality. Pricing is widely seen as an important policy tool. However, pricing has to be applied in a way that is efficient (with prices reflecting the marginal cost of each trip, including damage caused) and socially fair. Moreover, the issues of cost recovery and the use of public funds create a link between pricing and policy towards the financing of transport. There has been much research in this area in recent years. The challenge now is to present a systematic body of knowledge and practical procedures to those policy levels that have to implement the principles of pricing.