These are some sketches I have done recently.
It is good to note that the best models are sleeping models. If you get the "perfect sleeper", go for it. You might even want to extend your journey to some extra stops if your model is very interesting and still sleeping!
Sketching on the train
"No one ever attains eminent success by simply doing what is required of him: it is the amount of excellence of what is over and above the required that determines greatness"
-Charles Kendall Adams