CDL FINAL EXAM 2026/2027 QUESTIONS
AND ANSWERS
1. What is the minimum tread depth required for steering axle tires on a commercial vehicle?
A. 4/32 inch
B. 2/32 inch
C. 6/32 inch
D. 1/32 inch
Answer: A
Conceptual Explanation: Federal regulations require at least 4/32 inch tread depth on
steering tires; all other tires must have at least 2/32 inch.
2. What is the primary purpose of the tractor protection valve?
A. To increase braking force to the tractor
B. To control the speed of the air compressor
C. To prevent the engine from overheating
D. To keep air in the tractor if the trailer breaks away
,Answer: D
Conceptual Explanation: The tractor protection valve closes automatically if the trailer air
line breaks, preserving the tractor’s air pressure.
3. When driving a commercial vehicle, how far ahead should you typically look?
A. 2 to 5 seconds
B. 12 to 15 seconds
C. 20 to 25 seconds
D. 5 to 8 seconds
Answer: B
Conceptual Explanation: Commercial drivers are advised to look 12-15 seconds ahead,
which is about one city block or a quarter-mile on the highway.
4. Which of these is the correct way to test for hydraulic brake leaks?
A. Pump the brake pedal three times, then hold for five seconds
B. Drive at 5 mph and slam on the brakes
C. Check the fluid level after a long trip
D. Wait for the air pressure to reach 100 psi
Answer: A
, Conceptual Explanation: To check hydraulic brakes, pump the pedal 3 times and hold for
5 seconds; the pedal should not move.
5. What happens if the air pressure in the tanks falls below 60 psi?
A. The spring brakes will immediately lock
B. The engine will automatically shut down
C. The tractor protection valve will pop out
D. The low air pressure warning signal must come on
Answer: D
Conceptual Explanation: A low air pressure warning (usually a light and buzzer) must
activate before pressure drops below 60 psi.
6. When using the ‘snub braking’ method on a long downgrade, you should brake until your
speed is:
A. 5 mph below your ‘safe’ speed
B. 10 mph below your ‘safe’ speed
C. At the posted speed limit
D. 5 mph above your ‘safe’ speed
Answer: A
Conceptual Explanation: Brake until you are 5 mph below your safe speed, then release;
repeat as necessary to prevent brake fade.
AND ANSWERS
1. What is the minimum tread depth required for steering axle tires on a commercial vehicle?
A. 4/32 inch
B. 2/32 inch
C. 6/32 inch
D. 1/32 inch
Answer: A
Conceptual Explanation: Federal regulations require at least 4/32 inch tread depth on
steering tires; all other tires must have at least 2/32 inch.
2. What is the primary purpose of the tractor protection valve?
A. To increase braking force to the tractor
B. To control the speed of the air compressor
C. To prevent the engine from overheating
D. To keep air in the tractor if the trailer breaks away
,Answer: D
Conceptual Explanation: The tractor protection valve closes automatically if the trailer air
line breaks, preserving the tractor’s air pressure.
3. When driving a commercial vehicle, how far ahead should you typically look?
A. 2 to 5 seconds
B. 12 to 15 seconds
C. 20 to 25 seconds
D. 5 to 8 seconds
Answer: B
Conceptual Explanation: Commercial drivers are advised to look 12-15 seconds ahead,
which is about one city block or a quarter-mile on the highway.
4. Which of these is the correct way to test for hydraulic brake leaks?
A. Pump the brake pedal three times, then hold for five seconds
B. Drive at 5 mph and slam on the brakes
C. Check the fluid level after a long trip
D. Wait for the air pressure to reach 100 psi
Answer: A
, Conceptual Explanation: To check hydraulic brakes, pump the pedal 3 times and hold for
5 seconds; the pedal should not move.
5. What happens if the air pressure in the tanks falls below 60 psi?
A. The spring brakes will immediately lock
B. The engine will automatically shut down
C. The tractor protection valve will pop out
D. The low air pressure warning signal must come on
Answer: D
Conceptual Explanation: A low air pressure warning (usually a light and buzzer) must
activate before pressure drops below 60 psi.
6. When using the ‘snub braking’ method on a long downgrade, you should brake until your
speed is:
A. 5 mph below your ‘safe’ speed
B. 10 mph below your ‘safe’ speed
C. At the posted speed limit
D. 5 mph above your ‘safe’ speed
Answer: A
Conceptual Explanation: Brake until you are 5 mph below your safe speed, then release;
repeat as necessary to prevent brake fade.
