Using air brakes: stopping, braking and low pressure
Section 5.4 of the Kentucky CDL Manual (p. 5-8) covers how to use air brakes, from normal stops to low-pressure warnings. It is tested on the Air Brakes test.
Key facts
| Part of | the Air Brakes test (80% to pass) | KY CDL Manual, front section pp. 2-3 |
|---|---|---|
| Manual section | §5.4 Using air brakes | KY CDL Manual p. 5-8 |
| Questions in CDL Mile's bank | 24 | CDL Mile, checked against KY CDL Manual |
Key rules
- § 5.4.8p. 5-9
Setting the parking brakes on very hot brakes can damage them. Use wheel chocks on a level surface, and let the brakes cool before you use the parking brakes.
Parking Brakes
- § 5.4.8p. 5-9
Newer vehicles have a yellow, diamond-shaped knob labeled "parking brakes." Pull it out to apply the parking brakes and push it in to release them.
Parking Brakes
- § 5.4.8p. 5-9
Without automatic drains, you empty the air tanks yourself at the close of every working day. That clears out moisture and oil, which could otherwise make the brakes fail.
Parking Brakes
- § 5.4.3p. 5-8
In controlled braking you brake as hard as you can short of locking the wheels and keep steering movements very small. This keeps the vehicle straight while still letting you turn if needed.
Emergency Stops
- § 5.4.3p. 5-8
Controlled braking uses only very small steering movements. If you need to steer more, or the wheels lock, let off the brakes and put them back on as soon as you can.
Emergency Stops
Try two questions
Air Brakes · Using air brakes
Your brakes are very wet and the temperature is below freezing. Why should you avoid setting the parking brakes?
Tap an answer to see the explanation and the manual page.
Air Brakes · Using air brakes
Why can a heavily loaded vehicle need a long distance to stop when low air pressure makes the spring brakes come on?
Tap an answer to see the explanation and the manual page.
More Air Brakes topics
Sources
Kentucky Commercial Driver's License Manual, version March 2025, Kentucky State Police. Page references are to its printed page numbers. CDL Mile is independent and not affiliated with Kentucky State Police.
Updated for the March 2025 Kentucky CDL manual. Last checked November 5, 2026.
See where you stand on all three Kentucky tests.
A free 15-question check, then practice that targets your weak spots. $49 for 60 days if it helps.
Get my free score →