If the first thing you do is to apologize because you’ve already failed the first and most basic requirement, the rest of the interview might not matter. If you can’t even bother to show up to the interview on time, why should your interviewer expect you to be prompt if you actually get the job? Even if you have a good excuse, it’s still the worst possible way to set the right tone.
Take a dry run the night before and get there early. Sit in the parking lot and bone up on your interview questions. Just be there on time.