As an experienced train commuter chalking up a couple more thousand kilometers every month between my hometown of Gouda and my work in Amsterdam, I've pretty much perfected the art of nodding off while sitting erect.

Sometimes it happens without me even realizing it, for example while reading a book or just staring out the window. Sometimes I even feel it coming and resist or just let it happen.

The amazing thing is that although I nod off in a kind of semi-hypnotic imaginary dream world, I remain erect and do not fall over. The bumps and jerking motions shift my body slightly to the left and to the right, but I never end up in the lap of the passenger across from me nor on the shoulder of the person next to me.

On occasion I dream of eating and wake up with my mouth open and my jaws biting up and down. Or if it is hot and I'm drinking a refreshing ice-cold substance.

I've trained my mind to sleep but to be alert at the same time. I do not know exactly how this mechanism works, it is like clockwork. Although the train stops along the way, I do not wake up or at least I believe that I am not awake until just the right moment: when the conductor announces Station Gouda! And when this announcement is not made or the public announcement system has short-circuited? I still wake up.