you have to be mindful of how crowded the train is and try to keep as much space available for others as possible. That said, just head to the middle of the two-car sections and lean on it there. people don't usually stand in there, there is plenty of room, and you typically get all that space to yourself. I figured this out when I flatted a few blocks from union station and was too dumb to change my own tube--that problem's been resolved I'm happy to say.

You'll see a few other bikes going on the train and find some solace in the fact that it's not just you. watch what they do, adapt, and enjoy the ride.