Corrected entry: Platform Nine and Three Quarters is supposed to be a secret platform that only magical people can access. However when Harry, Ron and Hermione have boarded the train and are looking for a cabin we can see out of the window a GNER (Great North-Eastern Railway) train visible on the next platform. The train is most noticeable for its blue colour with a single red stripe running the length of the train.
Jazetopher
1st Oct 2006
Correction: The Hogwarts Express is very much the same as the Knight Bus that Harry takes to the Leaky Cauldron, in the sense that muggles cannot see it, even when in the same vicinity as other cars. The same principle applies for the train sitting on the platform at the station next to the real trains.
Jazetopher