NC CDL Combination Vehicles study guide
NC CDL Combination Vehicles · Work through your exam, one topic at a time.
The Combination Vehicles knowledge test is the Class A portion of North Carolina's commercial driver licensing knowledge exams. It is administered by the NCDMV and is taken by drivers who will operate a tractor-trailer, a truck towing a heavy trailer, or other vehicle combination whose towed unit exceeds 10,000 pounds gross vehicle weight rating. The NC CDL Combination Vehicles study guide has 7 sections and about 2,734 words.
01Driving Combination Vehicles Safely: Rollover Risks, Braking, and Speed Management
This domain tests how a tractor-trailer behaves at speed and under braking, and how the CDL exam expects you to trade speed for stability with a heavy, high-center-of-gravity combination. A combination vehicle carries its center of gravity higher than a car and rolls at a lower lateral force.
418 words, about 2 min02Trailer Sway, Off-Tracking, and Rearward Amplification
This domain covers the three geometry problems the exam tests: where the trailer's rear actually goes in a turn, how far the last trailer swings in a quick maneuver, and how to answer a trailer that starts oscillating. Rear axles cut a shorter path than the front axle.
386 words, about 2 min03Inspection of Combination Vehicles: Coupling System, Air Lines, and Landing Gear
This domain tests the combination-specific walk-around: the fifth wheel and kingpin, the air and electrical connections, and the landing gear - the items that fail and drop trailers. Jaws open, jaws and plate greased, mounting bolts tight, no cracks in the plate or its mount, release lever locked with the safety latch engaged.
371 words, about 2 min04Coupling and Uncoupling Procedures
This domain covers the sequence for joining a tractor to a trailer and separating them safely - the order of steps, the tug test, and the mistakes that drop a trailer. Inspect the fifth wheel and kingpin.
427 words, about 2 min05Air Brake System Operation in Combination Vehicles, Including Trailer Brakes and Antilock Brake Systems
This domain tests how tractor and trailer air systems share pressure, how to test them to the correct limits, and what ABS actually does. It isolates the tractor's air supply if a trailer line separates or the trailer breaks away, which sets the trailer's spring brakes.
367 words, about 2 min06Pintle Hooks, Doubles/Triples, and Other Combination Configurations
This domain covers the hardware that is not a standard fifth wheel: pintle hooks, converter dollies, and multi-trailer sets, plus how those configurations change handling. The pintle hook takes the lunette ring of a towed unit.
374 words, about 2 min07Cargo Securement and Weight Distribution for Combination Vehicles
This domain covers legal weight limits, how to shift weight between axles without creating a new overload, and the securement rules that apply to combination vehicles. Federal limits on the Interstate System: 80,000 lb gross, 20,000 lb on a single axle, 34,000 lb on a tandem group, all subject to the bridge formula.
391 words, about 2 min