This document discusses regulatory and contractual aspects of urban mobility systems. It begins by defining an urban mobility system and its key elements, including infrastructure, services, organizations, regulations, and agents. It then examines different decision levels in mobility systems and how introducing a new mode like bus rapid transit can change relationships between agents and objectives. The document outlines different types of organizations in the transport sector, including government agencies, service operators, and economic regulators. It also discusses regulatory frameworks, contractual relationships, and how contracts and performance indicators can be used to drive performance in urban mobility systems.