Double

The maneuver whereby a towboat with barges in tow must break the tow and push half of it into the lock chamber, lock that part through, and then enter the remaining barges with the towboat. In other words, two distinct lockage must be made to pass the entire tow of barges and towboat. Also called "double lockage." (TNDOT1)

(See also Rocky Mountain Double; Turnpike Double) A combination of two trailers pulled by a power unit. Usually refers to a power unit pulling two 28 foot trailers. (ATA2)