20"x87=1740" Divide that by 12 to get feet = 145' for the bridge.
A 72' bridge would be shorter than two 40' box cars. 72'x12=864" Divide that by 87 to get HO scale = 9.93" long.
Hope this helps,
i just ordered one of walthers' HO scalesingle track truss bridge kits and was wondering about its length in feet in HO scale. Walthers says its bridge is 20 inches long. would that be longer than 72 feet?