Kentucky CDL Combination study guide
Kentucky CDL Combination · Work through your exam, one topic at a time.
The Kentucky CDL Combination Vehicles knowledge test is the additional written exam a driver must pass - on top of the General Knowledge test - to obtain a Class A commercial driver's license that authorizes operating tractor-trailers, truck-and-trailer combinations, and similar articulated units. It is written for drivers who plan to pull a trailer for a motor carrier, an agricultural or construction operation, or their own business, and who therefore need to demonstrate combination-specific knowledge rather than general vehicle knowledge alone. The Kentucky CDL Combination study guide has 9 sections and about 2,589 words.
01Driving Combination Vehicles Safely
This domain checks whether you can manage a tractor-trailer as a system rather than drive it like a large car. Expect questions on pivot points, brake lag, mirror use, speed selection, and how trailer weight changes steering and stopping.
335 words, about 2 min02Air Brakes on Combination Vehicles
The exam tests your knowledge of the tractor-trailer air system: compressor and governor operation, dual reservoirs, low-pressure warning, spring brakes, leakage tests, and daily inspection of slack adjusters and hoses. The compressor builds pressure; the governor cuts it out and back in.
312 words, about 2 min03Antilock Braking Systems (ABS)
This domain covers how ABS prevents wheel lockup on tractors and trailers, what the dash and trailer lamps mean, and how to brake and steer when ABS activates. Wheel speed sensors feed the ECU, which pulses modulator valves to prevent lockup.
313 words, about 2 min04Coupling and Uncoupling
The exam tests the safe sequence for connecting and separating a tractor and trailer, including fifth wheel and kingpin inspection, the tug test, air line connection, landing gear, and trailer brake checks. Before coupling, inspect the fifth wheel, jaws, and kingpin for damage, wear, and secure mounting.
311 words, about 2 min05Inspecting Combinations
This domain checks your ability to inspect a tractor-trailer systematically: coupling hardware, air brakes, lights, tires, cargo securement, frame, hoses, and dolly components. Start with a walk-around: check tires, wheels, rims, lights, reflectors, mud flaps, and body damage.
252 words, about 1 min06Towing Trailers and Converter Dollies
This domain covers doubles and triples: converter dollies, coupling order, safety chains, air lines, electrical connections, shut-off valves, and the handling differences of multi-trailer combinations. A converter dolly has its own fifth wheel, axles, brakes, and often a safety chain or chains.
280 words, about 1 min07Braking and Skid Control with Combinations
This domain tests stopping distance, brake lag, controlled and stab braking, ABS use, skid recovery, and downgrade control in a tractor-trailer. Total stopping distance includes perception, reaction, brake lag, and actual braking.
263 words, about 1 min08Handling Combination Vehicles (Offtracking, Turns, Backing)
This domain tests offtracking, wide turns, swept path, mirror use, backing, pull-up maneuvers, and spotter communication. Offtracking means the rear wheels of the trailer follow a path inside the tractor's front wheels.
260 words, about 1 min09Rollover Prevention and Load Stability
This domain tests center of gravity, speed in curves, load securement, weight distribution, rearward amplification, and smooth evasive action to prevent rollover. A high center of gravity increases rollover risk.
263 words, about 1 min