Railway bosses will reveal their new-style trains next week.
The new Thameslink train will be displayed at London Blackfriars station on Tuesday, May 24
Thameslink runs the route from Bedford and Luton, through London and onto Brighton.
The company say the longer Class 700 trains will ease congestion on rush hour services.
Other features of the train include wide doors and aisles, wider walkways between carriages, and luggage stacks for fold-up Brompton bikes.
The trains also include intelligent climate-controlled air conditioning, electronic signs showing where there is space on board, screens with Tube updates, and fully accessible toilets for disabled passengers.