Double Trailer Trucks

Double trailer trucks are essentially a standard tractor trailer with an additional trailer attached. Double trailer trucks are often used when traveling long distances or when larger amounts of cargo must be delivered from one place to another. Certain types of double trailer trucks require special permits to drive, as handling is typically more difficult than a standard tractor trailer. Additionally, double trailer trucks may pose increased safety risks than standard tractor trailers.

Types of Double Trailer Trucks

In the United States, a standard double trailer truck consists of a tractor, or powered front of the truck, and two semi-trailers that measure 28.5 feet in length. Semi-trailers are named to indicate that when built to attach to a tractor, these trailers do not have front wheels like standard trailers. Therefore, the term semi-trailer indicates that these are essentially partial trailers. There are other types of double trailer trucks and longer combination vehicles (LCV).

Other types of double trailer trucks and other longer combination vehicles (LCV) include:

  • Turnpike double trucks, which consist of two 48-foot trailers that have a maximum weight of 147,000 pounds.
  • Rocky Mountain double trucks, which consist of one 40-to-53-foot trailer and one 28.5-foot trailer that have a maximum weight of 129,000 pounds. The smaller second trailer is often referred to as the “pup.”
  • In Canada, a turnpike double truck consists of two 53-foot trailers. A Rocky Mountain double truck consists of a 50-foot trailer and a 24-foot “pup” trailer.

Double Trailer Truck Safety Considerations

Research shows that double trailer trucks are innately more dangerous than standard tractor trailers. This is partly because the excess size of the vehicle is more difficult to manage and maneuver. A simple lane change needs more room, consideration, and caution for a double trailer truck than for a tractor trailer. For this reason, drivers of double trailer trucks should have more advanced driving skills and proceed with greater caution while on the road.

Double Trailer Movements

The movement of the second trailer in a double trailer truck may pose additional safety hazards not seen in a standard tractor trailer. When the driver makes a small turn such as a lane change, the movement may be amplified in the second trailer. This means that the second trailer may see a much larger shift in movement than was seen in the tractor and first trailer. This exaggerated sway may lead to a rollover of the second trailer or collision with other vehicles or items on the road.


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“Tractor Pulling Two Trailers Overturns.” States News Service 21 Sept. 2010. Academic OneFile. Web. 18 Oct. 2013.