The Metro or subway in Paris reminds me of what I used to do in the local Singapore MRT (Mass Rapid Transit). All I need is a small A5 sketchbook and my Hero pen with ink that flows faster than you can say "ink that flows faster than"… ok that was silly.
But since school is out and the local beaches during this cold winter climate is a no-no for model sketching, I look to the subways for train system sketching practices. It helps me focus on gestures because you never know when your model has to alight, looks in another direction or when the train gets so packed like a tin of sardines you don't need to hold the handles for stability because the people around you are pressed up so tightly against you. :)
Sketching in the subway also trains (no pun… really) you how to keep on track (Ok, this one I tried too hard for the pun) quickly at your model as many of them will be very conscious that you are drawing them. So if you are ever doing this and your model happens to be within a 3 metro range, start by looking elsewhere. When you peripheral vision tells you that he or she is not looking at you, glance at your model for a couple of seconds, and if you if your model will be looking back at you… casually turn your eyes away. :) So far only about 5% of the people are sketch are comfortable with me sketching them and no I have not been fined for stalking people. That's why it's an Art. :D
Enjoy! And have a restful and peaceful end of the year festive season!!