Instructions

Air Brakes

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice.. Read More

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Vermont Commercial Driver’s Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question 25

Passing Score 20

1. A safety valve is set to open at ____ pounds per square inch (psi).

100

150

200

The safety valve protects air tanks and the rest of an air brake system from accumulating too much air pressure. The safety valve is usually set to open at 150 psi.

2. Having ABS on only one axle:

Can be dangerous.

Still allows you additional control when braking.

Slows the vehicle, but cannot stop it.

If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer, or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.

3. Air tank drains should:

Only be used by mechanics.

Only be used when it is wet outside.

Be used to drain the tanks completely.

In an air brake system, air tank drains are used to remove water and compressor oil from the air tanks. When operating a drain, be sure to drain the tank completely.

4. What helps prevent wheel lockup when braking?

An Anti-Lock Braking System (ABS)

Air brakes

An alternator

The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.

5. What can happen if the air pressure gets too low in an air brake system?

The brakes may squeak.

The brakes may stop working.

The brakes may be sluggish.

Pressing and releasing the brake pedal unnecessarily can let air out of the braking system faster than the compressor can replace it. Air brakes may cease to work effectively if the pressure becomes too low.

6. While operating on a downgrade, you should brake until you reach a speed that is:

5 mph below your safe speed.

10 mph below your safe speed.

15 mph below your safe speed.

While driving downhill, you should hold down the brake pedal until your vehicle reaches a speed 5 mph below your safe speed, then release the brake pedal. Repeat this process.

Grade This Section