Help the frantic commuter complete his text message to his boss.

Please don't fire me, but I am currently ___ the wrong train. I will be at the office as soon as I find my way back!

The correct answer is on.

Romance language speakers often translate their native prepositions (like en in Spanish or French) directly to "in" for all vehicles. However, in English, we use on for public transportation where you can stand up and walk around (like a train, bus, or plane). We use in for private, enclosed vehicles where you must sit down to enter (like a car or a taxi).