The Starlight Straights are the maglev trains that connect the domes of Counterweight. The name is a (intentionally bad) pun on the geologic concept of a strait.
Some maglev trains exist off the Straights system, and spray down a lane of goop in front of them as a kind of "track". The Iron Choir owns some of these.
As of "I Am Not Allowed", Jorne runs a casino train line on the Starlight Straights. This seems to have done well, since he is subsequently able to leave his career at Snowtrak and remains successful as of the finale.