Not much has been seen of the Express line. However, it is known that is runs under a bridge on Thomas's Branch Line and that it has not been used for a while, due to Doc needing to remove weeds and apply fresh ballast on the track. It ends at Ulfstead Castle. It is currently unknown where it begins.
Donald, Douglas, James, and Doc were dispatched in 2011 to lay a fresh set of ballast leading up to Ulfstead Castle for its restoration. Sir Robert Norramby expressed a strong desire to run a mainland express service to and from the castle, so a small main line extension branches off past Thomas' Branch Line. This is so larger engines, like James and Connor, can be supported by stronger rails with broader curves.