In the year 5,000,000,029, the population of the main city of New New York, including the Senate, were killed by an airborne virus caused by a mood drug. Its final message to the nearby star systems was to keep away from New Earth. The only people who survived were the Face of Boe and Novice Hame, the latter surviving in the smoke produced by the former. They later controlled the Motorway. Hame looked after Boe, who in turn controlled the computer systems. However, the skeletons of the old Senators still remained.
In 5,000,000,053, 24 years later, after the Tenth Doctor first arrived on New Earth, the Doctor and Boe worked together to save the people in the Motorway, who proceeded to repopulate the main city of New New York, and the Senate was reestablished. (TV: Gridlock)