CDL · Air brakes
Under ideal conditions, how much total distance does a vehicle with air brakes need to stop from 55 mph?
Correct answer: More than 450 feet.
Answer options
- ARoughly 250 to 300 feet
- BLess than 200 feet
- CMore than 450 feet Correct
Why
Air brakes need about half a second of brake lag before they take hold, which adds roughly 32 feet at 55 mph to the perception, reaction and braking distances. Altogether, the stop takes more than 450 feet even on dry pavement with good brakes.
About this question
Topic: Air brakes License: CDL
Part of these practice sets:
Where it applies: Asked in every state.
Practice the whole set
This question is part of Checking and Using Air Brakes (15 questions). Take the full set and check your score.
Practice Checking and Using Air BrakesMore questions from Checking and Using Air Brakes
- What is the name for the sum of the perception, reaction, brake lag, and braking distances?
- Why do air brakes take longer to work than hydraulic brakes?
- With the engine shut off and the brakes released, a combination vehicle's air pressure should drop by less than:
- How do you set the parking brake on a newer vehicle equipped with air brakes?
- Once the spring brakes have been set, which of these is the right practice?
- In a vehicle equipped with air brakes, how do you make a normal stop?
- A combination vehicle's air system has been built up to governor cut-out. With the engine shut off and the brake pedal fully applied, the air pressure should drop by less than:
- Your truck's air tanks do not drain automatically. How often should you drain them yourself?
Practice on your phone.
Practice here in your browser, or use the app with the same questions and explanations. It's free on the App Store.