Utah CDL — Air Brakes Exam Simulation
25 questions · 20 correct to pass. You won't see any feedback until you finish — just like the real test.
Utah CDL — Air Brakes questions with answers
20 sample questions from the Utah CDL — Air Brakes question bank — each with the correct answer, a short explanation, and the section of the official handbook it comes from.
1. How often must you empty air tanks that have only manual drain valves?
Correct answer: When you finish driving for the day
Manually drained tanks need their water and oil released once you finish driving for the day.
Source: 5.1.4 Air Tank Drains
2. What is a key benefit ABS gives you during hard braking?
Correct answer: You can steer around an obstacle while braking
ABS may not stop you any faster, but by preventing lockup it lets you keep steering control to maneuver around a hazard.
Source: 5.4.2 Braking with Antilock Brakes
3. An air brake setup actually combines how many separate braking systems into one?
Correct answer: Three - the service, parking, and emergency brakes
The handbook explains that air brakes are really three systems working together: the service brake, the parking brake, and the emergency brake.
Source: Section 5 - Air Brakes (introduction)
4. What is the 'wig wag' found on some air-brake vehicles?
Correct answer: A mechanical arm that drops into view when pressure is low
The wig wag is a mechanical arm that swings into the driver's view when system pressure falls below 55 psi.
Source: 5.1.11 Low Air Pressure Warning
5. How large a crack in a brake drum makes it unsafe to keep in service?
Correct answer: A crack longer than half the width of the friction area
A drum or disc is unsafe once a crack runs longer than half the width of its friction surface.
Source: 5.3.2 Walk-around Inspection
6. Compared with a car's hydraulic brakes, how quickly do air brakes respond?
Correct answer: A little slower, since the air must travel through the lines
Hydraulic brakes act instantly, while air brakes have a short lag as the air travels out to each brake.
Source: 5.4.4 Stopping Distance
7. Before walking away from a parked commercial vehicle, what must you do?
Correct answer: Set the parking brakes or chock the wheels
An unattended vehicle can roll away, so you must set the parking brakes or chock the wheels.
Source: 5.4.8 Parking Brakes
8. Since which year have all newly built vehicles come with automatic slack adjusters?
Correct answer: 1994
The manual states that every vehicle built since 1994 comes with automatic slack adjusters.
Source: 5.3.2 Walk-around Inspection
9. Why shouldn't you keep driving until the spring brakes engage on their own?
Correct answer: You should stop while you can still control the brakes
When the low-air warning first appears, stop promptly while you still have brake control rather than waiting for the spring brakes to grab.
Source: 5.1.14 Spring Brakes
10. On a long, steep downgrade, the service brakes should be treated as what?
Correct answer: A supplement to the engine's braking effect
The manual stresses that on a steep grade the brakes only add to the slowing effect of the engine held in a low gear.
Source: 5.4.6 Proper Braking Technique
11. On large buses, the low-pressure warning devices commonly activate at about what pressure?
Correct answer: 80 to 85 psi
For big buses, these warning devices commonly trip much earlier, around 80 to 85 psi.
Source: 5.1.11 Low Air Pressure Warning
12. What is the defect most often found during roadside inspections?
Correct answer: Brakes that are out of adjustment
The handbook notes that out-of-adjustment brakes are the defect inspectors turn up most often at roadside checks.
Source: 5.3.2 Walk-around Inspection
13. At 55 mph on dry pavement, roughly how much extra distance does air brake lag add?
Correct answer: About 32 feet
According to the manual, that lag tacks on roughly 32 feet of travel at 55 mph on dry roads.
Source: 5.4.4 Stopping Distance
14. On a newer air-brake vehicle, how do you set the parking brakes?
Correct answer: Pull the yellow, diamond-shaped knob out
Newer vehicles use a diamond-shaped yellow push-pull knob; pulling it out applies the spring/parking brakes and pushing it in releases them.
Source: 5.1.15 / 5.4.8 Parking Brakes
15. Which of these is required equipment on every vehicle with air brakes?
Correct answer: A low-air-pressure warning signal
A low-air-pressure warning signal is mandatory on air-brake vehicles; the other items listed are optional add-ons.
Source: 5.1.11 Low Air Pressure Warning
16. During stab braking, when should you reapply the brakes after releasing them?
Correct answer: As soon as the wheels start rolling again
In stab braking you release when the wheels lock, then reapply fully only once the wheels begin turning again.
Source: 5.4.3 Emergency Stops
17. Using the recommended snub-braking method downhill, about how long should each brake application last?
Correct answer: Roughly three seconds
You apply firmly to slow about 5 mph below your safe speed and then release; each of these applications should last roughly three seconds.
Source: 5.4.6 Proper Braking Technique
18. The visible low-air warning must switch on before tank pressure drops below what level?
Correct answer: 55 psi
A required warning you can see must activate before the air pressure falls under 55 psi.
Source: 5.1.11 Low Air Pressure Warning
19. A manual slack adjuster probably needs adjusting if it moves more than about how much at the push-rod connection?
Correct answer: One inch
If a slack adjuster moves more than roughly one inch at the push-rod connection, it likely needs to be adjusted.
Source: 5.3.2 Walk-around Inspection
20. Total stopping distance with air brakes is made up of how many separate factors?
Correct answer: Four
The four pieces are perception distance, reaction distance, the brake lag distance, and braking distance.
Source: 5.4.4 Stopping Distance