What does the train metaphor from Bob Dylan song mean?

The train is often depicted as a symbol of travel, movement, and change. In Bob Dylan's song, 'The Lonesome Death of Hattie Carroll', this imagery emphasizes Hattie Carroll's tragic destiny - a sudden change resulting in an untimely death.

"And the judge says you have killed / But now your punishment must be / Just to let your mother pray / And fill your head with rocks

Then they took her to the graveyard / And they laid her in the grave / There she rests in peace at last"