At one time, and they may still be there, signs throughout the lower train level say distances in feet to the various terminals and the Marriott.

I recall, walking eastbound from A to D/E, the first sign says some 5,000+ feet. 5,280 is one mile.

Years ago, when I smashed bags for UA, we operated out of A (way before the CO merger). We also ground handled the daily LH to FRA. By way of vehicle on airfield, it was roughly one mile between A and D (then called IAB, Mickey Leyland Int'l Arrivals Building).