Please give me a general meaning of what up the train or down the train means? does it mean to be in front of it. Would you give me another example of up the * or down the *?
Moving up and down something can be tricky because the actual direction changes based on the object. Up tends to mean toward the beginning, or toward the entrance, or toward the source, or toward the parts that are perceived as higher and down is the opposite direction. The phrase is only used when there are two obvious directions, although which direction is "up" and which direction is "down" may not be obvious.
A native speaker wouldn't say "He walked down the room." but would say instead "He walked across the room." I could say "I walked a mile down the road before I saw anyone." or "I ran up the road to see what happened." and either would be correct. Sometimes it isn't obvious whether you should use "up" or "down" and I think in those cases either will work.
Some examples: "She walked up the assembly line to find the source of the jam." Up in this sentence means she walked toward the beginning of the assembly line. "He moved up the corporate ladder." - he was promoted to a position closer to the head of the company. "The girl walked down the aisle to find her seat in the theater." - she moved away from where she entered and also, many theaters have a floor that slopes down toward the stage.
I've never used the expression "up the train", but I imagine it means toward the engine and "down the train" would mean toward the last car.