Delaware CDL Air Brake Test (DE) 2026

5 out of 5 (52 votes)
80% Passing score
20 Questions
4 Mistakes allowed
As a Delaware driver preparing for your commercial driver's license, mastering air brakes is a crucial step. Our Delaware DMV practice test provides a comprehensive selection of 20 multiple-choice questions, meticulously designed to cover every aspect of air brake systems. Dive into the specifics of compressors, reservoirs, and brake chambers while also understanding the operational principles and essential safety protocols. This Delaware air brakes CDL test ensures you grasp the critical components and their functions, enabling you to drive safely and efficiently. One of the unique challenges of air brake systems is the brake lag time. Our CDL air brake test includes questions addressing this vital factor, helping you understand how to account for it when calculating stopping distances. With the Delaware DMV air brake test, you will be well-prepared to handle real-world driving situations that require precise braking knowledge. To achieve a passing score on the Delaware CDL air brakes practice test, you'll need to correctly answer at least 16 out of the 20 questions. This scoring requirement ensures that you have a thorough understanding of the material, preparing you for the official DMV test and your future on the road. Each question in the Delaware DMV test practice is tailored to the specific rules and regulations of Delaware, ensuring your preparation is state-specific and relevant. Our Delaware DMV practice test is conveniently accessible online through various platforms, including mobile, desktop, and mobile apps. This accessibility allows you to study and practice anytime, anywhere, fitting your preparation into your schedule with ease. At the end of each Delaware drivers license test practice session, you'll receive a detailed summary of your performance. This summary highlights the questions you answered incorrectly and provides the correct answers, helping you learn and improve with each attempt. Prepare confidently with our Delaware DMV air brake test, designed to equip you with the knowledge and skills needed for safe and effective air brake operation. By thoroughly understanding the air brake system and its components, you'll be on the right track to securing your commercial driver's license in Delaware.
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Sample Delaware Air Brakes Test Questions

Question 1

Which sequence correctly describes stab braking during an emergency stop?

  1. A Apply the foot brake and trailer hand valve continuously until stopped
  2. B Lock the wheels, then release the brakes for the same amount of time they were locked
  3. C Apply the brakes fully, release them when the wheels lock, and reapply fully when the wheels roll again
  4. D Pump the brake pedal rapidly using light pressure

Correct answer: C – Apply the brakes fully, release them when the wheels lock, and reapply fully when the wheels roll again

With stab braking, apply the brakes completely and release them if the wheels lock. Reapply the brakes fully as soon as the wheels begin rolling again. Reapplying before the wheels roll can prevent the vehicle from straightening out.

Source: Delaware Commercial Driver’s Manual — § 5.4.3, “Emergency Stops”

Question 2

Under normal conditions, when should the parking brakes be applied on an air-brake vehicle?

  1. A Only during vehicle inspections
  2. B Whenever the vehicle is parked
  3. C Only when parking on a grade
  4. D While slowing the vehicle in traffic

Correct answer: B – Whenever the vehicle is parked

The Delaware manual directs drivers to use the parking brakes whenever they park. Do not use them when the brakes are extremely hot or very wet in freezing temperatures because damage or freezing may result. In those exceptional conditions, secure the vehicle with wheel chocks and allow the brakes to cool or dry as directed.

Source: Delaware Commercial Driver’s Manual — § 5.4.8, “Parking Brakes”

Question 3

Which condition is a warning that air brakes may be fading on a downgrade?

  1. A Less pedal pressure is needed to maintain the same speed
  2. B The pedal feels spongy when first applied
  3. C Increasing brake application pressure is needed to maintain the same speed
  4. D The vehicle accelerates after the brake pedal is released

Correct answer: C – Increasing brake application pressure is needed to maintain the same speed

Needing progressively more application pressure to maintain the same speed indicates possible brake fade. Slow down and shift to a lower gear. Increased pressure can also indicate brakes that are out of adjustment, air leaks, or other mechanical problems that require attention.

Source: Delaware Commercial Driver’s Manual — § 5.1.10, “Application Pressure Gauge”

Question 4

In an air-brake system, what is a “wig wag”?

  1. A A mechanical arm that drops into view to warn of low air pressure
  2. B A device that adjusts slack automatically
  3. C A component of the brake-light circuit
  4. D A lever used to drain the air tanks

Correct answer: A – A mechanical arm that drops into view to warn of low air pressure

A wig wag is a low-air-pressure warning device that lowers a mechanical arm into the driver’s view. The manual describes it operating when system pressure drops below 55 psi. An automatic type rises when pressure exceeds 55 psi, while a manual-reset type must be returned to its normal position by hand.

Source: Delaware Commercial Driver’s Manual — § 5.1.11, “Low Air Pressure Warning”

Question 5

During the CDL low-air warning test, the signal must activate before tank pressure drops below:

  1. A 80 psi
  2. B 55 psi
  3. C 40 psi
  4. D 20 psi

Correct answer: B – 55 psi

The Delaware manual requires the low-air warning signal to activate before pressure falls below 55 psi. In a dual system, use the tank with the lowest pressure when checking the warning. If the warning fails, the driver may not know that usable braking pressure is being lost.

Source: Delaware Commercial Driver’s Manual — § 5.3, “Inspecting Air Brake Systems—Test Low Pressure Warning Signal”, 49 CFR § 393.51(c) — Warning signals, air pressure and vacuum gauges

Question 6

A dual air-brake system has two circuits commonly called the primary and secondary systems.

  1. A True
  2. B False

Correct answer: A – True

A dual air-brake system consists of two separate systems operated by a single set of controls. One is called the primary system and the other the secondary system. Each has its own tanks, hoses, and lines, and both supply air to the trailer when one is attached.

Source: Delaware Commercial Driver’s Manual — § 5.2, “Dual Air Brake Systems”

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