Aim of the paper is to illustrate an ontology based approach to the design of mobility information systems which, through multiple distribution channels, provide companies and individual consumers with the information that facilitate their mobility in a metropolitan area. Main advantages of the proposed approach are user queries whose semantics is independent of the system implementation, and the possibility of delegating user tasks to mobile software agents by means of either PCs or PDAs. The ontology framework also facilitates data collection and control of remote devices such as semaphores and signs. The outlined architecture is under experimentation for managing mobility in the Catania metropolitan area.