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Doubles and Triples (Longer Combination Vehicles: LCV)

Last Updated: Nov 11, 2015

What New Drivers Need To Know About Doubles & Triples CDL Endorsement:

Doubles and triples (LCV's) are combinations of multiple trailers attached to one truck, as opposed to standard 5-axle semi's.

A separate CDL endorsement will be required for drivers to pull 2 trailers (doubles) or 3 trailers (triples) at the same time.

CDL drivers will be required to pass a specific knowledge test to get their doubles-triples endorsement, and the doubles-triples endorsement will be indicated with a 'T' on a driver's CDL.

It is illegal in many states to pull triple trailers.

Doubles and triples are also known as Longer Combination Vehicles (LCV).

What Are Doubles and Triples?

Simply, pulling two or three trailers at the same time with a single tractor (truck).

Length and weight limits may vary by state, and certain lengths of LCV's will require driving only on highways or turnpikes.

How Do Drivers Get LCV Endorsements?

CDL drivers will be required to pass a separate knowledge exam to be legally allowed to pull doubles or triples. TruckingTruth always recommends that drivers get ALL endorsements available when getting their CDL , in order to maximize their opportunities.

The exam will cover:

  • Procedures for assembly and hookup of the units;
  • Proper placement of heaviest trailer;
  • Handling and stability characteristics including off-tracking, response to steering, sensory feedback, braking, oscillatory sway, rollover in steady turns, and yaw stability in steady turns; and
  • Potential problems in traffic operations, including problems the motor vehicle creates for other motorists due to slower speeds on steep grades, longer passing times, possibility for blocking entry of other motor vehicles on freeways, splash and spray impacts, aerodynamic buffeting, view blockages, and lateral placement.

Does The Doubles-Triples Endorsement Require A Road-Skills Test?

Currently, there are no states that are known to require a road test for doubles-triples endorsement.

What Are the Regulations Regarding Doubles and Triples?

The Surface Transportation Assistance Act of 1982 (STAA), was a policy funding act of the Federal government that, among other things, established minimum and maximum length restrictions on commercial motor vehicles (CMV's).

The STAA also established a National Network of highways designated for use by large trucks, on which federal width and length rules apply. The National Network (NN) includes most of the Interstate Highway System along with other specified non-interstate highways.

States are required to allow doubles combinations of 28 feet each in length on the NN, with the overall length of the trailer combination to be a maximum of 65 feet.

Federal weight limits on the National Network are set at 80,000 lbs, and special permits will be required for hauling over 80,000 lbs on the NN.

Weight limits on CMV's, including doubles and triples, are also calculated on a weight-to-length basis, according to number of axles, trailer configuration, and weight on each axle.

See Also: Bridge Formula Weights Calculator

Additional State Regulations For Doubles and Triples:

Aside from regulations contained in the STAA:

  • Individual states cannot set maximum CMV weight at lower than 80,000 lbs on the NN. They can, however, specify their own requirements on their own roads outside of the National Network.
  • Additional weight and length restrictions will vary by state, so drivers will need to check state regulations when pulling LCV's.
  • Certain states will only allow certain combinations on certain routes within their state, outside of the NN.
  • Each state may also require specific permits to haul doubles and triples through them. Drivers will need to plan their trip accordingly, and be aware of specific state regulations on their route.

What Should Drivers Know About Pulling Doubles-Triples?

Generally, there are four categories that drivers will need to pay careful attention to when pulling doubles-triples:

  • Pulling Doubles and Triples:

    There are issues that are specific to pulling doubles and triples that CDL drivers will need to keep in mind at all times such as increased risk of rollover, greater distance required for stopping and changing lanes, more actual space needed, and parking considerations.

  • Coupling and Uncoupling:

    Additional trailers will be connected using a special converter dolly, which is basically a coupling device consisting of a fifth wheel mounted on one or two axles. Drivers will need to know and understand specific coupling and safety concerns to properly transport doubles and triples.

  • Inspecting Doubles and Triples:

    Doubles and triples will include more items to inspect, both more of the normal items that a driver would inspect, with some additional inspection points. The increase in critical parts means an increased level of inspection.

    Additional checks for doubles and triples include additional electric and air lines, additional fifth wheels, safety chains secured to each trailer, and basically an entirely new coupling system.

  • Doubles and Triples Air Brake Check:

    In addition to normal pre-trip inispection of the air brake system, drivers will need to make sure that the system is working for all trailers when pulling doubles and triples.

See Also: Double/Triple Trailers Training Program


Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Combination Vehicle:

A vehicle with two separate parts - the power unit (tractor) and the trailer. Tractor-trailers are considered combination vehicles.

Commercial Motor Vehicle:

A commercial motor vehicle is any vehicle used in commerce to transport passengers or property with either:

  • A gross vehicle weight rating of 26,001 pounds or more
  • A gross combination weight rating of 26,001 pounds or more which includes a towed unit with a gross vehicle weight rating of more than 10,000 pounds
  • DOT:

    Department Of Transportation

    A department of the federal executive branch responsible for the national highways and for railroad and airline safety. It also manages Amtrak, the national railroad system, and the Coast Guard.

    State and Federal DOT Officers are responsible for commercial vehicle enforcement. "The truck police" you could call them.


    Commercial Motor Vehicle

    A CMV is a vehicle that is used as part of a business, is involved in interstate commerce, and may fit any of these descriptions:

    • Weighs 10,001 pounds or more
    • Has a gross vehicle weight rating or gross combination weight rating of 10,001 pounds or more
    • Is designed or used to transport 16 or more passengers (including the driver) not for compensation
    • Is designed or used to transport 9 or more passengers (including the driver) for compensation
    • Is transporting hazardous materials in a quantity requiring placards


    Commercial trade, business, movement of goods or money, or transportation from one state to another, regulated by the Federal Department Of Transportation (DOT).


    Refers to pulling two trailers at the same time, otherwise known as "pups" or "pup trailers" because they're only about 28 feet long. However there are some states that allow doubles that are each 48 feet in length.

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