"expected additional capacity"

You wrote, "Transport chiefs plan to use the expected additional capacity created by passengers moving onto HS2 to improve local and regional services between Birmingham and Rugby."

FROM:  https://www.business-live.co.uk/economic-development/plans-long-term-rail-improvements-27648499?utm_source=businesslive_newsletter&utm_campaign=west_midlands_newsletter2&utm_medium=email

The "expected additional capacity" simply means more space, more choice of where to sit, on the intercity trains for passengers not going to London or Brum Airport.  They cannot use HS2 because it is too fast to stop at Rugby, Coventry and Birmingham International stations.  In fact, won't HS2 mean fewer intercity trains because London and Brum Airport passengers are expected to use HS2?  Or, the present intercity trains might have more stations to stop at so the intercity service becomes slower?  Certainly, a second class provision with HS2 being the main, most important intercity service in England.

Please put me right, Tamlyn.