The train between Ba Sing Se and Omashu is run entirely by earth benders, who work in shifts to keep the train running all day. They also act as security forces in case of trouble. There is a prison car in the train for just such an incident. The entire train is made of stone, to allow earth benders to move it, but the seats are padded and comfortable. Every seat has a table, for whatever one might use it for, and if you are riding during meal time hours, a meal is served.

Train rules
The train can only be in one place at a time, do not attempt to board the train unless you are in a train station, and the conductor has opened the doors for boarding.
When the train is in motion, you can’t get off, and you do not control when the train arrives.
Tosatsu is the train. This includes all the NPCs on board. He will decide when the train has left the station, and when it arrives.