You probably didn't travel halfway around the world to sit in your hotel room, so it's important to know what to expect when using the loo on the go. Trains, buses and airlines will usually be equipped with some kind of bathroom, though toilets differ depending on your location and how modern the mode of transportation is. For instance, most airplanes have a Western or American-style commode, built into the back wall of the restroom, and these flush using a vacuum rather than water.
Trains are still popular for transportation globally, and while most trains will certainly have facilities, the type of toilet you end up with on board will tend to reflect whatever the local toilet tradition is. So while travelling through India or parts of rural Thailand, it's likely you'll find a squat toilet, sometimes leading down to an exhilarating view of the tracks flying by, though some are quite nice, especially if you can afford a first-class ticket [source: O'Neill]. Subways aren't quite the same as traditional trains, so be prepared to use the toilet facilities normally available in the station. Reviews of the cleanliness regarding such facilities don't tend to be favorable, and in many parts of Europe and Asia, these stops will still cost you money. Try to think ahead. Finally, be aware that older trains may not have on-board toilets in every instance, so be prepared to do your business before a lengthy trip!