Wiktionary
prep.phr. (context simile UK English) With unstoppable momentum.
Usage examples of "like a train".
The car was heavy and sluggish, but stable: at speed, it cornered like a train.
It was like a train going in and out of tunnels and that was like the noise of the boys eating in the refectory when you opened and closed the flaps of the ears.
When Lebel had finished his relation of the message from London, the men round the table had let out a collective sigh, like a train arriving at its platform after a long journey.
I think she was so busy with her thoughts, her mind was like a train pulling too many cars.
In fact the night sky seemed to Kate to be like a train of restless, irritable horses, their traces flapping and slapping in the wind.
My recent tour of the world had all been Overmantles, which is more like a train.
Everything went dark and she was aware of another room rushing at her like a train.