Delaware CDL — Air Brakes practice
Delaware CDL — Air Brakes: Safe Driving Practices practice test
Following distance, scanning, blind spots, using your lights, and the habits that prevent crashes and keep you in control.
Content reviewed against official driver handbooks · August 12, 2026
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12 sample Safe Driving Practices questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
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1. Two of your brakes are out of adjustment as you work down a long grade. What does the manual say happens to the others?
Correct answer: They pick up the extra load and can overheat and fade
Every brake has to do its share. Brakes that are out of adjustment quit doing theirs first, leaving the rest to overheat and fade until there may not be enough braking to control the vehicle.
Source: Delaware Commercial Driver's Manual — Section 5.4.5, Brake Fading or Failure
2. You are about to troubleshoot a brake adjustment problem on a vehicle with automatic slack adjusters. What does the manual say to consult first?
Correct answer: That manufacturer's service manual, since adjusters from different makers do not all work alike
Automatic slack adjusters come from several manufacturers, and they don't all operate identically, so the manual points you to the service manual for the specific make.
Source: Delaware Commercial Driver's Manual — Section 5.3.2, During Step 5 Walk-around Inspection
3. In a dual air brake system, which of these does each of the two systems have for itself?
Correct answer: Its own air tanks, hoses and lines
The two systems are separate, each with its own tanks and plumbing, but the driver works both through one set of brake controls.
Source: Delaware Commercial Driver's Manual — Section 5.2, Dual Air Brake
4. You want to know whether your truck was built late enough that ABS was required. Where does the manual tell you to find its date of manufacture?
Correct answer: On the certification label
Air-braked truck tractors had to have ABS starting with those built March 1, 1997, and other air-braked vehicles a year later. The certification label carries the build date.
Source: Delaware Commercial Driver's Manual — Section 5.1.16, Antilock Braking Systems (ABS)
5. According to Delaware's manual, what is the air brake check on the inspection test designed to confirm?
Correct answer: That the safety devices work correctly as air pressure falls from normal to low
Air brake safety devices vary from vehicle to vehicle, so the check steps the pressure down to prove each one acts when it should. The manual notes that losing air pressure makes the emergency brakes activate, bringing an abrupt, uncontrolled stop.
Source: Delaware Commercial Driver's Manual — Section 11.1.2, Air Brake or Hydraulic Brake Check
6. On a vehicle with air brakes, what takes the place of the hydraulic brake check in Step 7 of the seven-step inspection?
Correct answer: The final air brake check laid out in the Air Brakes section
Section 2's Step 7 includes a hydraulic leak test. For air-braked vehicles, the manual substitutes the final air brake check: governor cut-in and cut-out, leakage rate, low pressure warning, automatic spring brake application, pressure buildup, and the parking and service brake tests.
Source: Delaware Commercial Driver's Manual — Section 5.3.3, Step 7 Final Air Brake Check
7. Each time you let up on the brake pedal, what happens to the air in the system?
Correct answer: Some of it escapes, so tank pressure falls until the compressor replaces it
Releasing the brakes vents some compressed air, which lowers the pressure in the tanks. The compressor then has to make up the loss.
Source: Delaware Commercial Driver's Manual — Section 5.1.7, The Brake Pedal
8. During the emergency brake test on Delaware's inspection test, your vehicle has valves that do not pop out by design. How do you tell that the parking or emergency brakes have applied?
Correct answer: Listen for air discharging from the air system
As you keep fanning off air, the parking or emergency brake valve normally pops out somewhere between 20 and 45 psi. Where the valves are not the pop-out kind, the sound of air leaving the system is the sign the brakes have set.
Source: Delaware Commercial Driver's Manual — Section 11.1.2, Air Brake or Hydraulic Brake Check
9. Your truck has rolled to a smooth, routine stop at a red light. What does the manual's normal-stop procedure have you do next?
Correct answer: Select a starting gear
For a normal stop, you press the pedal and control the pressure for a smooth stop, keep the clutch out until engine speed is near idle, and then pick a starting gear once stopped.
Source: Delaware Commercial Driver's Manual — Section 5.4.1, Normal Stops
10. You begin the air leakage rate test with the system fully charged and the engine off. What do you do with the parking brake?
Correct answer: Release it by pushing the control in
For the leakage test, the engine is shut off and the parking brake is released, with the wheels chocked if needed, before the pressure drop is timed.
Source: Delaware Commercial Driver's Manual — Section 5.3.3, Step 7 Final Air Brake Check
11. In an emergency, you manually adjust an automatic slack adjuster so you can get off the road. Why does the manual treat this as only a temporary measure?
Correct answer: The brake is likely to drift out of adjustment again soon, because the real fault has not been fixed
The manual allows manual adjustment of an automatic adjuster only as a stopgap in an emergency. It usually does not cure the underlying problem, so the brake will probably be out of adjustment again before long.
Source: Delaware Commercial Driver's Manual — Section 5.3.2, During Step 5 Walk-around Inspection
12. A converter dolly was built after March 1, 1998. What does the manual say it is required to have?
Correct answer: An ABS malfunction lamp on its left side
Vehicles with ABS use yellow malfunction lamps. On trailers the lamp is on the left side at a front or rear corner, and dollies built from that date on must carry one on the left side as well.
Source: Delaware Commercial Driver's Manual — Section 5.1.16, Antilock Braking Systems (ABS)
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