It often signifies the journey of life, the passage of time, and the interconnectedness of all things.
With all these train strikes all over the place, I'm not so sure about the interconnectedness of things.
No wonder MK prefers the scooter, like me
What I found found interesting, though, was a point he made about trains (I can't remember which interview it was): the idea was that cities will change, and come and go, and it doesn't really matter where he lives, but the railway lines between them remain constants in his life.