An inexplicable truth about New Yorkers is that they do not want to see you while riding the subway. Your roommate doesn't want to see you, your casual acquaintance doesn't want to see you, your priest doesn't want to see you, that guy you slept with two weeks ago certainly doesn't want to see you, your bartender doesn't want to see you, your mom doesn't want to see you, and most of all your coworker does not want to see you. Anyone you have ever spoken one word to in life would rather not run in to you on the subway. Here's the general rule: the fewer words that have been exchanged between yourself and someone, the less you two will want to run into each other down there. On the other side of the spectrum, the only two who may be an exception to this rule are your crush (if you are looking good) and your best friend. Otherwise, you just want to stay in your own world, locked in to sweet solitude and not forced to uphold some sort of unspoken social contract. It's not personal, it's just that we need this time packed into a crowded subway car to be alone, and we weren't expecting to see you here.
I go with the ignore option whenever practicable. I have slipped quietly out of a car a couple of times. And I've been genuinely delighted to see someone on the train less than 10 times in the last ten years. (Far less).