The train is like an arrow of time that rushes forward and never goes back...

Arrow of the time
Dashing from the past through the present, and rushing into the future.
It travels through ages, tells the story from the past, and record the story in the future

Therefore, when the train leaving platform, it is like an arrow shot from its bow dashing forward until reaching the target

The train is still running...

Time continues moving forward...

The Arrow of Time still does its..... job.