In my experience, this shuttle runs fairly frequently on weekdays (I never seem to have to wait more than a few minutes).

Is it the same story on weekends? I'll be taking an Amtrak train arriving at BWI at 7:52 on a Saturday night and will have a flight leaving at 8:55 - how frequently will the shuttles be running?

If it's very delayed for some reason, are there usually cabs waiting at the station?

Yonatan