The Buenos Aires Underground has one of the most diverse metro fleets in the world, and has had some of the oldest models in operation on any network. The network began with a relatively standardised fleet, but throughout its over 100-year-long history, it has seen numerous purchases which have created cases where some lines operate numerous models. Recently there have been increased efforts to modernise and standardise the fleets, with large purchases from China CNR Corporation and Alstom.
