It takes four hours because they are on different Islands that aren't near each other or connected well. You are insinuating that it is just a slow train.
There isn't much you can do other than spend tens of billions building a bridge or tunnel. Cars often get the ferry to make that journey.
A train has to travel in the opposite direction, across several islands and then back up. 4 hours is pretty good considering that. Even then there is so little demand for this journey it is infrequent.