I always leave my apartment at least 90 minutes before I'm scheduled for an interview even if I know traveling will only take me 40 minutes or so.
There's so much to deal with like trains and delays on them. I don't mind if I get to the interview early. It gives me a chance to take a look at the area and see if there's anything interesting there.
But once I left my apartment 90 minutes early for an interview and there was some kind of police action on the subways so I was sitting on the same train for over an hour.
I was horrified knowing I was going to be late. Thank goodness the train was above ground at the time and my cell phone worked. I called the person I had to meet with and explained the situation. He was so nice and said her heard about the problem on the news and told me that he'd see me whenever I arrived.
Finally I got there but I was an hour late. I know her appreciated the fact that I called him.