Being opaque about your reasons for tardiness never hurts, as Moy clearly points out, and a profuse apology seems to go a long way. But when it comes down to it, you might want to emphasize a healthy night's sleep, as some experts suggest cancelling the interview altogether in the event of unforeseen circumstances. This should come as no surprise, as research shows 70% of executives would discount an applicant if they show up to an interview late.
Tactfully apologizing seems to be a best-practice here, and notifying the hiring manager as quickly as possible is always the right course, as Kristi Jones, manager of talent acquisition for human resources at H&R Block says: "Don’t call several hours later or even the next day...Your chances of getting the interview rescheduled decrease greatly.”
Follow these steps, and don't forget to set your alarm for an early morning interview. Otherwise you'll be a master at crafting apologetic emails and getting hired by the skin of your teeth. Oh yeah, and never forget to polish that resume.
[h/t The Daily Muse]