This paper focuses on the use of vague discourse in planning. Early contributions identified vagueness as a ‘problem’ to be solved so as to avoid potential misunderstandings and conflicts. This paper adopts the complementary point of view whereby vagueness can also be a ‘resource’, that is, a strategy used by actors in adverse circumstances. A systematic analysis of the texts and illustrations of 36 urban transport plans shows that vagueness is an essential ingredient. It is used mainly as a way to hedge against unwanted public commitments in the context of major uncertainties and tension between actors.