Summary: Boe has done all he can to preserve some of the planetâs population.
They’re all seeking the end of their long journey, the motorway’s exit, always believing others must have reached the terminus. The dream keeps them going, year after year; the hope of reaching their destination, of getting out into fresh air, where there are jobs to be had and a life to live.
In truth they’ll just go around and around, because the journey is all that’s keeping them alive. Everyone on the surface is long gone; the travellers in the under-city are the only survivors, and Boe will keep them down there, protected, until the Doctor comes to save them.