The subway

The subway is a means of transportation that—oh, well, I'm not going to tell you the whole story of how this machine came to be.
But all you know is that it's a place you frequent on your way to and from work. Nothing strange has ever happened to you other than a guy dressed as Spider-Man.

To reach another dimension, you'll need to be in a completely empty carriage or one packed with people. In either case, you'd never be seen disappearing just like that.

When you change direction, the driver is different; the crowd you crashed into at every turn disappears or is replaced by new people.

You can go from a world where there's a multidimensional being sitting in the middle of the city like a pole to a universe where all men are REALLY BOY-
Sorry, the thing is that you can go from an apocalyptic world to an invented fantasy one.

The train station will be the same, you would just have to go down the stairs and get on the line, it's the same train, you never know what's going to happen or where it's going to take you.