CDL GENERAL KNOWLEDGE TEST
QUESTIONS AND ANSWERS
1. When inspecting your vehicle’s tires, which of the following conditions is considered a
major defect that requires taking the vehicle out of service?
A. A tread depth of 3/32 inch on the steering axle tires.
B. Fabric showing through the sidewall.
C. Mismatched tire sizes on the same axle.
D. Tire pressure 5 PSI below the recommended level.
Answer: B
Conceptual Explanation: According to federal regulations, any tire with fabric or cord
showing through the tread or sidewall is a major defect. Steering axle tires require at least
4/32 inch tread depth, while others require 2/32 inch. A measurement of 3/32 on a
steering tire is also a violation, but fabric exposure is an immediate safety hazard.
2. Which of the following statements regarding retarders is true?
A. Retarders are most effective when the road is slippery or icy.
B. Retarders reduce the need for downshifting on long downgrades.
,C. Retarders apply braking force to all wheels, including the steering axle.
D. Retarders can cause the drive wheels to skid when traction is poor.
Answer: D
Conceptual Explanation: Retarders apply braking power to the drive wheels only. On
slippery surfaces, this braking force can cause the drive wheels to lose traction and skid,
potentially leading to a jackknife. You should turn the retarder off in wet, icy, or snowy
conditions.
3. How far ahead should a commercial driver be looking while driving at highway speeds?
A. 1/8 of a mile.
B. 20 to 30 seconds.
C. 5 to 8 seconds.
D. 1/4 of a mile.
Answer: D
Conceptual Explanation: Drivers should look 12 to 15 seconds ahead. At highway speeds,
this distance is approximately 1/4 of a mile.
4. When using the ‘snub braking’ technique on a long downgrade, you should apply the
brakes until your speed has dropped to:
A. A complete stop.
B. 10 mph below your ‘safe’ speed.
, C. The speed limit of the road.
D. 5 mph below your ‘safe’ speed.
Answer: D
Conceptual Explanation: The correct snub braking technique involves braking until you
are 5 mph below your set safe speed, releasing the brakes, and then repeating the process
when your speed returns to the safe speed.
5. What is the ‘bridge formula’ designed to prevent?
A. Overheating of brakes on steep grades.
B. The risk of tipping over in high winds.
C. Structural damage to bridges and roads due to weight concentration.
D. Hydroplaning on wet surfaces.
Answer: C
Conceptual Explanation: The bridge formula permits less maximum axle weight for axles
that are closer together to prevent overloading bridges and road surfaces.
6. In the event of a rear-wheel acceleration skid, what is the correct recovery procedure?
A. Apply the brakes firmly to regain control.
B. Countersteer in the opposite direction of the skid.
C. Stop accelerating and push in the clutch.
QUESTIONS AND ANSWERS
1. When inspecting your vehicle’s tires, which of the following conditions is considered a
major defect that requires taking the vehicle out of service?
A. A tread depth of 3/32 inch on the steering axle tires.
B. Fabric showing through the sidewall.
C. Mismatched tire sizes on the same axle.
D. Tire pressure 5 PSI below the recommended level.
Answer: B
Conceptual Explanation: According to federal regulations, any tire with fabric or cord
showing through the tread or sidewall is a major defect. Steering axle tires require at least
4/32 inch tread depth, while others require 2/32 inch. A measurement of 3/32 on a
steering tire is also a violation, but fabric exposure is an immediate safety hazard.
2. Which of the following statements regarding retarders is true?
A. Retarders are most effective when the road is slippery or icy.
B. Retarders reduce the need for downshifting on long downgrades.
,C. Retarders apply braking force to all wheels, including the steering axle.
D. Retarders can cause the drive wheels to skid when traction is poor.
Answer: D
Conceptual Explanation: Retarders apply braking power to the drive wheels only. On
slippery surfaces, this braking force can cause the drive wheels to lose traction and skid,
potentially leading to a jackknife. You should turn the retarder off in wet, icy, or snowy
conditions.
3. How far ahead should a commercial driver be looking while driving at highway speeds?
A. 1/8 of a mile.
B. 20 to 30 seconds.
C. 5 to 8 seconds.
D. 1/4 of a mile.
Answer: D
Conceptual Explanation: Drivers should look 12 to 15 seconds ahead. At highway speeds,
this distance is approximately 1/4 of a mile.
4. When using the ‘snub braking’ technique on a long downgrade, you should apply the
brakes until your speed has dropped to:
A. A complete stop.
B. 10 mph below your ‘safe’ speed.
, C. The speed limit of the road.
D. 5 mph below your ‘safe’ speed.
Answer: D
Conceptual Explanation: The correct snub braking technique involves braking until you
are 5 mph below your set safe speed, releasing the brakes, and then repeating the process
when your speed returns to the safe speed.
5. What is the ‘bridge formula’ designed to prevent?
A. Overheating of brakes on steep grades.
B. The risk of tipping over in high winds.
C. Structural damage to bridges and roads due to weight concentration.
D. Hydroplaning on wet surfaces.
Answer: C
Conceptual Explanation: The bridge formula permits less maximum axle weight for axles
that are closer together to prevent overloading bridges and road surfaces.
6. In the event of a rear-wheel acceleration skid, what is the correct recovery procedure?
A. Apply the brakes firmly to regain control.
B. Countersteer in the opposite direction of the skid.
C. Stop accelerating and push in the clutch.
