As much as I have flown AA over the years, I have never flown through Dallas. Well, that changes today. I have a tight connection (about 50 minutes) where I arrive in terminal B (B2 right now) and leave from terminal A (A24). What is the fastest way to get from terminal to terminal - can I walk (I am a fast walker) or is there a train or bus that I should catch?

In advance, I appreciate those who will help me with this question. Happy flying!