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CDL · Driving with Air Brakes

When braking with air brakes during normal driving, what is the recommended technique?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Apply steady, controlled pressure (with modern ABS, do not pump); for non-ABS, brake firmly without locking the wheels

  1. A Pump the brakes rapidly
  2. B Never use the brakes
  3. C Apply steady, controlled pressure (with modern ABS, do not pump); for non-ABS, brake firmly without locking the wheels
  4. D Slam the brakes hard always

Why this is the answer

For NORMAL stops with air brakes, apply STEADY, CONTROLLED pressure. With ABS (Antilock Braking System), do NOT pump the brakes — apply firm, steady pressure and let the ABS prevent lockup. For older non-ABS systems, brake firmly without locking the wheels (controlled braking) or use 'stab braking' in emergencies (apply fully, release when wheels lock, reapply). CDL air brakes.

Air brake lag: there's a slight delay before air brakes take effect (about 1/2 second), so account for it. Knowing proper braking technique (steady pressure, don't pump with ABS) is commonly tested.

Source: FMCSA CDL Manual — Air Brakes, Braking Technique

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About this topic: Driving with Air Brakes

Driving a vehicle with air brakes is different from driving one with hydraulic brakes: there is brake lag of up to half a second, stopping distance includes that lag, the low-air warning must never be ignored, and spring brakes will apply on their own if pressure drops too far. These questions cover braking technique, stopping distance and what to do when the system warns you. This is one of 4 Air Brakes questions on driving with air brakes, each with a full explanation on a single study page.

New to this exam? Our CDL exam guide explains the format, scoring, and how to prepare.

Related questions

Driving with Air Brakes

What is 'brake lag' in an air brake system?

 Driving with Air Brakes

On a vehicle with anti-lock braking systems (ABS), what should the driver do during hard braking?

 Driving with Air Brakes

What is the proper procedure for an emergency stop using air brakes if the vehicle does NOT have ABS?

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