a transport system, spec. a network of public passenger transport within urban areas.

British. An overground railway. Also more generally: public transport operating above the ground. Cf. underground, adj. 3.

Any netlike or complex system or collection of interrelated things, as topographical features, lines of transportation, or telecommunications routes…

A transport system linking a city centre with its suburbs or with surrounding towns; (also) an intercity air shuttle service. Chiefly as a proper…