A Commuter Sketch on Car 9230

I got off work early and made the 6:30 PM express train to Stamford on Track 21 at the Grand Central Terminal.  A young couple preferred standing by the closed doors of Car# 9230 we were on.  Adjacent to them was a seated passenger.  All of them in my front view.  I thought a trio of the figures would be a nice composition.  I started with the seated one, then worked next on the young lady before the next train stop at the125th Street station.  Additional passengers came on board and the young couple got momentarily separated and pushed away from my view.  As much as I wanted to include her partner in this sketch, I resisted making up one.  I put away the sketchbook into my backpack and browsed the Internet on my phone.  It's hard knowing when to stop.  I'm still trying to learn that but I think I succeeded this time..