Chrome has magnetic properties.
A bunch of people are on a train presumably made of metal.
You see where I'm going with this ;)
The idea is for Chrome to see the train and hop onto it by attaching to the side with his Magnetic Ability. It would presumably make a loud noise since he's made of a moderately heavy metal.
I'll wait for someone who's on the train to approve this idea before I butt into the storyline.