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Friday, April 10, 2009

A Beginner's Guide to CDL Endorsements: Double and Triple Trailers

Drivers have been required to have a Commercial Driver's License (CDL) to drive a Commercial Motor Vehicle (CMV) since April 1, 1992. The Federal Highway Administration (FHWA) develops and issues standards for testing and licensing CMV drivers. Among other requirements, states are allowed to issue CDLs only after the driver passes knowledge and skills tests administered by the state that relate to the type of vehicle the driver wants to operate.

Drivers need CDLs if they are in interstate, intrastate, or foreign commerce and drive a vehicle that meets one of the definitions of a CMV. Drivers who operate special types of CMVs need to pass additional tests to obtain the necessary endorsement(s) on their CDL. Endorsement T is for drivers who operate CMVs with double or triple trailers (triple trailers are illegal in some states). Double and triple trucks are also known as Longer Combination Vehicles (LCVs). A knowledge test is required.

To obtain a double/triple trailers endorsement, applicants must have knowledge of:
  • Procedures for assembly and hookup of the units
  • Proper placement of the 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
  • 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 of blocking entry of other motor vehicles on freeways, splash and spray impacts, aerodynamic buffeting, view blockages, and lateral placement.

    The U.S. Department of Transportation (DOT) Federal Motor Carrier Safety Administration (FMCSA) has developed minimum training requirements for operators of LCVs. There are also special requirements for classroom and skills instructors who train LCV drivers. For purposes of this training, an LCV is defined as any combination of a truck-tractor and two or more trailers or semi-trailers that has a gross vehicle weight rating greater than 80,000 pounds and operates in interstate commerce. Twin trailers, also known as western doubles, are not subject to this rule, because they have a gross vehicle weight rating of 80,000 pounds or less. These rules were effective June 1, 2004.

    LCV training consists of both driving and non-driving activities. Non-driving activities include activities such as route planning and checking cargo and weight. There are different training courses for LCV doubles and triples because they have different operating characteristics.

    To qualify for doubles training, drivers must show six months of driving experience in vehicles with a Gross Combination Weight Rating (GCWR) of 26,001 or more pounds. For the triples training, drivers must show six months of truck-tractor/semitrailer or twin-trailer experience.

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