What's currently happening in London is the sub-surface lines are GoA 1 (i.e., "a train system with signals") and are moving to GoA 2 (i.e., "the train drives itself from station to station unless the driver intervenes").

The new deep-level stock (i.e., New Tube for London) is specified to be able to be retrofitted with GoA 4 equipment (i.e., "there are no staff on the train, driver, attendant, or otherwise"), but will start out as GoA 2 (Victoria, Central, Northern, and Jubilee lines are already fitted and run as such with their existing stock).