CDL General Knowledge Test practice questions
237 free questions with answers and explanations.
- 1.What is the correct procedure to test the trailer service brakes using the trailer hand valve?Combination Vehicles (if applicable)
- 2.During a pre-trip inspection, a driver observes that the fifth wheel skid plate has deep gouges and cracks. What is the most appropriate action?Combination Vehicles (if applicable)
- 3.During a pre-trip inspection, a driver finds that the red (emergency) glad hand on the tractor is leaking air when disconnected from the trailer. What does this indicate?Combination Vehicles (if applicable)
- 4.When performing a pre-trip inspection, a driver notices that the spring brakes on the trailer are not applying when the emergency air line (red glad hand) is disconnected. What does this indicate?Combination Vehicles (if applicable)
- 5.A driver is inspecting the air brake system of a combination vehicle. After building full air pressure, the driver applies the service brake. What is the maximum allowable air pressure drop in one minute for a combination vehicle?Combination Vehicles (if applicable)
- 6.A driver is backing a combination vehicle and needs to turn the trailer to the left. To initiate this maneuver, how should the driver initially steer the tractor?Combination Vehicles (if applicable)
- 7.A driver is preparing to uncouple a combination vehicle. After lowering the landing gear until it makes firm contact with the ground, what is the next critical step?Combination Vehicles (if applicable)
- 8.When inspecting the fifth wheel assembly of a combination vehicle, what is the significance of worn or missing fifth wheel grease?Combination Vehicles (if applicable)
- 9.When driving a combination vehicle, what is the most effective way to prevent a trailer from 'jackknifing' during hard braking on a slippery surface?Combination Vehicles (if applicable)
- 10.A driver is preparing to back a combination vehicle into a dock. To minimize the risk of 'jackknifing', what is the most important principle to follow?Combination Vehicles (if applicable)
- 11.A driver is coupling a tractor to a semi-trailer on a slight incline. After backing under the trailer, what is the most critical step to perform BEFORE raising the landing gear?Combination Vehicles (if applicable)
- 12.What is the primary danger of 'bobtailing' (driving a tractor without a trailer) on slippery surfaces compared to driving a loaded combination vehicle?Combination Vehicles (if applicable)
- 13.During a pre-trip inspection of a combination vehicle, a driver finds that the fifth wheel skid plate has deep gouges and cracks. What is the appropriate action?Combination Vehicles (if applicable)
- 14.When driving a combination vehicle, what is the primary reason for keeping the tractor and trailer in a straight line while backing?Combination Vehicles (if applicable)
- 15.A driver is inspecting the air lines of a combination vehicle. Which of the following conditions indicates a serious problem that requires immediate attention before driving?Combination Vehicles (if applicable)
- 16.What is the primary danger of coupling a tractor to a trailer on an uneven surface?Combination Vehicles (if applicable)
- 17.A driver is inspecting the brake chamber pushrods on a combination vehicle. The maximum allowable brake stroke for a Type 30 brake chamber is 2 inches. If the pushrod extends 2.25 inches when the brakes are applied, what does this indicate?Combination Vehicles (if applicable)
- 18.A driver is inspecting the electrical cable connecting the tractor to the trailer. What is the most critical item to look for to ensure proper light and brake signal function?Combination Vehicles (if applicable)
- 19.A driver is inspecting the kingpin and fifth wheel assembly. What is a critical sign of wear or damage that would render the coupling unsafe?Combination Vehicles (if applicable)
- 20.During a pre-trip inspection, a driver notices that the service (blue) glad hand on the tractor is leaking air when connected to the trailer. What is the most appropriate action?Combination Vehicles (if applicable)
- 21.A driver is inspecting the air tank drain valves on a combination vehicle. What is the primary purpose of draining the air tanks daily?Combination Vehicles (if applicable)
- 22.When inspecting the electrical cable connecting the tractor to the trailer, what is an acceptable condition?Combination Vehicles (if applicable)
- 23.A driver is driving a combination vehicle and notices that the trailer wheels are locking up prematurely during moderate braking. Which of the following is the most likely cause?Combination Vehicles (if applicable)
- 24.What is the primary danger of driving a combination vehicle with an improperly secured or absent kingpin locking pin (safety latch)?Combination Vehicles (if applicable)
- 25.A driver is maneuvering a combination vehicle through a tight turn. To avoid 'off-tracking' (trailer cutting the corner), what is the most effective technique?Combination Vehicles (if applicable)
- 26.A driver is performing a pre-trip inspection on the air brake system of a combination vehicle. After ensuring the air tanks are full and the engine is off, the driver applies the service brake and holds it. The air pressure gauge drops from 120 psi to 118 psi in one minute. What does this indicate?Combination Vehicles (if applicable)
- 27.A driver is preparing to couple a tractor to a semi-trailer. After backing the tractor under the trailer, what is the NEXT critical step before raising the landing gear?Combination Vehicles (if applicable)
- 28.What is the recommended procedure for checking the trailer's emergency brakes during a pre-trip inspection?Combination Vehicles (if applicable)
- 29.A driver is inspecting the air lines connecting the tractor to the trailer. What is the most critical condition to check for on the glad hand seals?Combination Vehicles (if applicable)
- 30.When performing a pre-trip inspection on a combination vehicle, a driver finds that the fifth wheel locking jaws are not fully closed around the kingpin. What is the immediate action the driver should take?Combination Vehicles (if applicable)
- 31.What is the primary danger of driving a combination vehicle with a bobtail tractor (no trailer) compared to driving a solo tractor or a full combination?Combination Vehicles (if applicable)
- 32.A driver is preparing to uncouple a combination vehicle. After lowering the landing gear until it makes firm contact with the ground, what is the next crucial step before completely separating the tractor from the trailer?Combination Vehicles (if applicable)
- 33.When backing a combination vehicle, what is the most effective way to correct a 'jackknife' situation once it has started?Combination Vehicles (if applicable)
- 34.You are backing a combination vehicle and need to turn right. To initiate the turn, which way should you initially turn the steering wheel?Combination Vehicles (if applicable)
- 35.A driver is inspecting the air lines connecting the tractor to the trailer. What is the most important characteristic to check for regarding the glad hand seals?Combination Vehicles (if applicable)
- 36.A driver is performing a pre-trip inspection on a combination vehicle's air brake system. After building full air pressure, the driver applies the service brake and holds the pedal down. For a tractor-trailer combination, what is the maximum acceptable air pressure drop in one minute for the service brakes?Combination Vehicles (if applicable)
- 37.A driver needs to perform a 'tug test' after coupling a tractor to a semi-trailer. What is the correct procedure for this test?Combination Vehicles (if applicable)
- 38.A driver is inspecting the air lines (hoses) connecting the tractor to the trailer. Which of the following conditions would indicate a need for immediate repair or replacement?Combination Vehicles (if applicable)
- 39.Which of the following scenarios is most likely to cause 'rearward amplification' in a combination vehicle?Combination Vehicles (if applicable)
- 40.A driver notices a distinct 'chucking' or 'surging' motion in the combination vehicle, especially during acceleration or deceleration. What is the most likely cause?Combination Vehicles (if applicable)
- 41.During the uncoupling process, after you have lowered the landing gear and disconnected the air lines and electrical cable, what is the next step before pulling the tractor forward?Combination Vehicles (if applicable)
- 42.A driver is performing a pre-trip inspection on a combination vehicle. When checking the service brake air lines, what is an acceptable maximum air pressure drop for a fully charged system (engine off, brakes applied)?Combination Vehicles (if applicable)
- 43.During a pre-trip inspection, a driver notices that the service (blue) glad hand is leaking air. What is the immediate action the driver should take?Combination Vehicles (if applicable)
- 44.When inspecting the fifth wheel assembly of a combination vehicle, what is the significance of worn or missing kingpin locking jaws?Combination Vehicles (if applicable)
- 45.A driver is performing a pre-trip inspection of the air brake system on a combination vehicle. After building full air pressure, the governor cut-out pressure should be between:Combination Vehicles (if applicable)
- 46.During a pre-trip inspection of a combination vehicle, a driver notices that the glad hand seals are cracked and brittle. What is the immediate consequence of this condition?Combination Vehicles (if applicable)
- 47.What is the primary function of the 'emergency' air line (red glad hand) in a combination vehicle air brake system?Combination Vehicles (if applicable)
- 48.You are inspecting the air lines on a combination vehicle. Which of the following conditions would immediately put the vehicle out of service?Combination Vehicles (if applicable)
- 49.A driver is inspecting the fifth wheel assembly of a combination vehicle. What is the most critical aspect to confirm regarding the locking jaws?Combination Vehicles (if applicable)
- 50.A driver is attempting to back a combination vehicle into a tight dock. To achieve the sharpest turn with the trailer, where should the driver look primarily?Combination Vehicles (if applicable)