These systems vary quite a bit around the globe. Very often multi-modal, they provide different integration opportunities across services: while some cities provide fare integration citywide, in others, all services compete as independent alternatives. While some cities have relied on the operations of private companies, others maintain this responsibility within a public agency. Planning, operating and controlling a public transport system, which is the focus of this document, is very challenging. Several actors with different goals are involved: the authorities, users, non-users, and operators. And not all users or non-users are identical since their traveling needs vary significantly in space and time. They are also different in their socioeconomic characteristics, which affects their choices: gender, age, income, knowledge of the system, and disabilities. Also, users and non-users interact in the city in a space that is increasingly limited: road congestion and limited vehicular capacity implies that each traveler’s decision will affect the experience of many others. The urban context in which all this activity happens is very dynamic and often unpredictable, so such key elements as demand and travel times follow inherently stochastic time-dependent patterns.