Texas CDL endorsements (Air Brakes, Combination,
HazMat)
ENDORMENT 1: AIR BRAKES Questions 1–40
1. What is the primary purpose of the air compressor in an air brake system?
A. Apply braking force
B. Store compressed air
C. Build and maintain air pressure
D. Control brake timing
Correct Answer: C
Rationale:
The air compressor supplies and maintains the air pressure needed for the entire braking system
to function.
2. What happens if air pressure drops too low in an air brake system?
A. Brakes apply automatically
B. Brakes release completely
C. Vehicle accelerates
D. Steering locks
Correct Answer: A
Rationale:
Air brake systems are designed so that low air pressure causes the brakes to apply automatically
as a safety feature.
3. What is the minimum air pressure required before driving most air brake
vehicles?
A. 60 psi
B. 80 psi
C. 100 psi
D. 120 psi
,Correct Answer: C
Rationale:
Most air brake systems require at least 100 psi to ensure proper braking capacity.
4. What device stores compressed air until it is needed for braking?
A. Air compressor
B. Brake chamber
C. Air tank (reservoir)
D. Slack adjuster
Correct Answer: C
Rationale:
Air tanks store compressed air so brakes can be applied even if the compressor is not actively
pumping.
5. What is “brake lag”?
A. Delay between pedal application and brake response
B. Reduced stopping distance
C. Excessive braking force
D. Brake overheating
Correct Answer: A
Rationale:
Air brakes experience a slight delay due to air travel time, making stopping distances longer than
hydraulic brakes.
6. Why do air brake vehicles require greater following distance?
A. Heavier loads
B. Brake lag
C. Larger mirrors
D. Steering limitations
Correct Answer: B
,Rationale:
Brake lag increases stopping time, requiring additional space to stop safely.
7. What component converts air pressure into mechanical force to apply the
brakes?
A. Air tank
B. Brake chamber
C. Slack adjuster
D. Foot valve
Correct Answer: B
Rationale:
Brake chambers use air pressure to move a pushrod that applies braking force.
8. What is the function of the slack adjuster?
A. Store air
B. Increase brake speed
C. Adjust distance between brake shoes and drum
D. Cool the brakes
Correct Answer: C
Rationale:
Slack adjusters maintain proper brake adjustment as components wear.
9. What condition indicates an out-of-adjustment brake?
A. Tight pedal feel
B. Excessive pushrod travel
C. High air pressure
D. Quiet braking
Correct Answer: B
Rationale:
Excessive pushrod travel reduces braking effectiveness and indicates improper adjustment.
, 10. Which brake type uses powerful springs to apply the brakes when air
pressure is lost?
A. Service brakes
B. Drum brakes
C. Spring brakes
D. Hydraulic brakes
Correct Answer: C
Rationale:
Spring brakes apply automatically when air pressure drops, serving as parking and emergency
brakes.
11. Why should spring brakes never be used while driving except in
emergencies?
A. They increase fuel usage
B. They apply suddenly and can cause loss of control
C. They wear tires
D. They reduce air pressure
Correct Answer: B
Rationale:
Spring brakes apply with full force and can cause skidding or jackknifing.
12. What does the air governor control?
A. Brake timing
B. Compressor cut-in and cut-out pressure
C. Air tank volume
D. Brake chamber size
Correct Answer: B
Rationale:
The governor controls when the compressor starts and stops pumping air.
HazMat)
ENDORMENT 1: AIR BRAKES Questions 1–40
1. What is the primary purpose of the air compressor in an air brake system?
A. Apply braking force
B. Store compressed air
C. Build and maintain air pressure
D. Control brake timing
Correct Answer: C
Rationale:
The air compressor supplies and maintains the air pressure needed for the entire braking system
to function.
2. What happens if air pressure drops too low in an air brake system?
A. Brakes apply automatically
B. Brakes release completely
C. Vehicle accelerates
D. Steering locks
Correct Answer: A
Rationale:
Air brake systems are designed so that low air pressure causes the brakes to apply automatically
as a safety feature.
3. What is the minimum air pressure required before driving most air brake
vehicles?
A. 60 psi
B. 80 psi
C. 100 psi
D. 120 psi
,Correct Answer: C
Rationale:
Most air brake systems require at least 100 psi to ensure proper braking capacity.
4. What device stores compressed air until it is needed for braking?
A. Air compressor
B. Brake chamber
C. Air tank (reservoir)
D. Slack adjuster
Correct Answer: C
Rationale:
Air tanks store compressed air so brakes can be applied even if the compressor is not actively
pumping.
5. What is “brake lag”?
A. Delay between pedal application and brake response
B. Reduced stopping distance
C. Excessive braking force
D. Brake overheating
Correct Answer: A
Rationale:
Air brakes experience a slight delay due to air travel time, making stopping distances longer than
hydraulic brakes.
6. Why do air brake vehicles require greater following distance?
A. Heavier loads
B. Brake lag
C. Larger mirrors
D. Steering limitations
Correct Answer: B
,Rationale:
Brake lag increases stopping time, requiring additional space to stop safely.
7. What component converts air pressure into mechanical force to apply the
brakes?
A. Air tank
B. Brake chamber
C. Slack adjuster
D. Foot valve
Correct Answer: B
Rationale:
Brake chambers use air pressure to move a pushrod that applies braking force.
8. What is the function of the slack adjuster?
A. Store air
B. Increase brake speed
C. Adjust distance between brake shoes and drum
D. Cool the brakes
Correct Answer: C
Rationale:
Slack adjusters maintain proper brake adjustment as components wear.
9. What condition indicates an out-of-adjustment brake?
A. Tight pedal feel
B. Excessive pushrod travel
C. High air pressure
D. Quiet braking
Correct Answer: B
Rationale:
Excessive pushrod travel reduces braking effectiveness and indicates improper adjustment.
, 10. Which brake type uses powerful springs to apply the brakes when air
pressure is lost?
A. Service brakes
B. Drum brakes
C. Spring brakes
D. Hydraulic brakes
Correct Answer: C
Rationale:
Spring brakes apply automatically when air pressure drops, serving as parking and emergency
brakes.
11. Why should spring brakes never be used while driving except in
emergencies?
A. They increase fuel usage
B. They apply suddenly and can cause loss of control
C. They wear tires
D. They reduce air pressure
Correct Answer: B
Rationale:
Spring brakes apply with full force and can cause skidding or jackknifing.
12. What does the air governor control?
A. Brake timing
B. Compressor cut-in and cut-out pressure
C. Air tank volume
D. Brake chamber size
Correct Answer: B
Rationale:
The governor controls when the compressor starts and stops pumping air.
