Physical length of the Freight units The U.S.A. standard is 45 feet in length, which can hold two 20 foot, one 40 foot container, or one 45 foot container, plus if hardened can be double stacked for twice the load. The BorderTransportationSystem is a High-Speed system and thus needs the front and back sides of the freight carrier to be somewhat streamlined.  It is recommended that the maximum container size be 20 feet, with 2.5 feet on both front and rear of the flat-bed container carrier being 45 or more feet.  Index of ... Physical Sizes of Containers