When you’re doing something like reading or writing, time passes without you knowing. It’s not that it actually moves any faster or slower—after all, the clock is not looking at you to determine when it should tick—but you don’t notice it.
I’ll ask you this: If you have enough spare attention to watch the clock, are you focused enough on your work? No. Especially when you’re on the train or expecting something to happen, get busy. Don’t let valuable minutes of your life disappear into the abyss because you were waiting.