Subway-pictures need to be a little askew in my opinion. It can help to top up the speed you try to capture like on photo No1.
If the photo is out of alignment you can feel the swell en wobbling of the train like in photo No2.
The photo can also give you the impression of moving forward, like on the last pic in this set of three; If the building-silhouettes would stand square in the frame, this pic would be merely some urban landscape on a bad print. Captured the skew way it’s a road-movie photograph behind a scratched window of some train. Which it is, of course (photo No3).
Keep you updated soon!