Weekday afternoons are typically quiet. Trains don't come very often and they are usually spotted with college students, mothers with small children, and the odd professional traveling from one site to another.
Rush hour, morning or evening, can be mad, especially if the trains are running behind. We pack in tightly, trying desperately not to touch one another, and uncomfortably sway with the stop and go of the train. I know many other cultures find it peculiar that Americans are so protective of personal space, and maybe we are a bit too squeamish, but I would rather keep the distance and wait for the next train, than to pack in like the commuters in Tokyo:
"In fact early morning rush hour gets so bad in Tokyo’s major central stations that a lot of them employ ‘pushmen’, armed with white gloves and the directive to make people fit in a carriage regardless of any sense of comfort or humanity."
My favorite time to travel on the metro is around 8 p.m.; rush hour is over and it is too early for the happy hour crowd to be stumbling home. The train is peppered with tired people traveling home after working late. It's quiet and we are all sympathetic to one another's general air of fatigue.
Late nights are completely different. Obviously, the later the hour the louder the train; on a weekends it often gets sloppy. Saturday night, after Ryan and I saw Batman: The Dark Knight, we were traveling from Bethesda to Friendship Heights. As we waited, we watched all sorts of people in various stages of intoxication. Our favorite was the girl picture below (though you can't see much of her.) Luckily, a kind stranger shook her awake as her train approached. She was completely out.
(quote and Tokyo photo from http://www.lo-la.co.uk/2008/05/08/train-tetris/#more-193)
