STAA doubles
STAA doubles or double pups are a type of long [combination vehicle] in the United States. They are named for the Surface Transportation Assistance Act of 1982. Each trailer is long and wide. The doubles are connected via a dolly. This long combination vehicle is the only combination of trailers allowed nationwide in the United States. The axle weight allowed is per single axle. STAA doubles make up less than 3% of the freight trailer fleet in the United States.