Thanks for visiting my blog.
I can draw standing in a moving train, because:
1. The trains over here ride quite smoothly. No bumpy ride.
2. Eventhough I am standing in the aisle, my back usually can lean on the side of the seat. It depends on where I stand of course. If I am fortunate enough to stand right beside a seat, then I can just turn around and lean on it. It provides a good support and stability when I am drawing.
3.I hold my small sketchbook in such a way that one end is resting on my tummy (for stability). While I am drawing my subject using pen/pencil, I usually don’t let my arm rest on the sketchbook nor the part of the seat behind my back and arm. Without anykind of support for it (except a bit from my shoulder), my arm/hand can move freely and doesn’t get affected by occasional bumps from the train. It can sort of ‘expect’ and follow/react on the motion of the train. And I get less (or none) ‘unexpected’ wild lines on my sketchbook.

Hopefully you understand what I wrote above. A bit tough to explain without any real life demo.
And I hope that it help you a bit.
My post “Trein” will show you how the seats are arranged, and help you understand my explanation better.

Cheers,
Evy

mary