Coordinating transport and urban planning is considered a necessity in urban policies. Most of the time, academic research focuses on the tools used to achieve this goal, and on their limits. We consider instead coordination in practice, as a result of action and not as one of its assigned objectives. Our study is based on a comparative analysis of six projects of the covering of transport infrastructure. These objects, at the crossroads between urban transport and planning policies, are considered both to reduce the nuisance associated with the transport infrastructure and to create new land surface. A system of interdependencies between the two fields of action (transport and urban planning) emerges from the design and construction of the covers. Coordination appears where it is not expected, from the succession of different operations, and structured through contractual and organizational instruments that still leave a large space for negotiation. It can also emerge in the technical design of projects or their operational management.