If your connection is tight, and the tram is just leaving the station when you get out of the tunnel, you can actually make it to the tram stops at the far ends of terminal A, using the moving walkways, at the same time the tram does (if you waited for the tram). So although it may seem quicker to walk, wait for the tram and arrive a little refreshed. FYI, terminal A is about 1 mile long end to end.

So if your gate is between the center and ends, it will be faster to walk than wait for the train. If you have time, bring a Sharpie and sign a rock!!