Alabama CDL — Air Brakes: Speed & Space Management Practice Test

Question 1

On a dual air system, the low air warning should come on before pressure drops below 55 psi in which system?

Accepted Answer

Either system — The warning light and buzzer should activate before pressure falls under 55 psi in either the primary or the secondary system, and if that happens while driving you should stop and park safely.

Answer

Only the primary system

Answer

Only the secondary system

Answer

Only the trailer supply system

Question 2

Before driving a vehicle with a dual air system, how much pressure should you let build up in both the primary and secondary systems?

Accepted Answer

A minimum of 100 psi in both systems — You should allow the compressor time to build a minimum of 100 psi in both the primary and secondary systems before you drive.

Answer

At least 55 psi in only one system

Answer

Exactly 150 psi in the primary system

Answer

Any pressure above 20 psi is enough

Question 3

For a vehicle with air brakes, total stopping distance is made up of which four parts?

Accepted Answer

Perception, reaction, brake lag, and braking distance — Because of brake lag, total stopping distance for air brakes adds four parts together: perception distance, reaction distance, brake lag distance, and braking distance.

Answer

Perception, reaction, cornering, and coasting distance

Answer

Following, merging, braking, and reaction distance

Answer

Idle, cut-in, cut-out, and braking distance

Question 4

If one half of a dual air system loses most of its pressure, what should you expect?

Accepted Answer

It will take longer to stop the vehicle — With one system very low, either the front or the rear brakes will not be fully operating, so it will take you longer to stop; bring the vehicle to a safe stop and have it repaired.

Answer

The parking brakes will release automatically

Answer

The remaining system will double its power

Answer

The brakes will lock up immediately

Question 5

What best describes a dual air brake system?

Accepted Answer

Two separate air systems sharing one set of controls — A dual air brake system is two separate air brake systems that share a single set of brake controls, with each system having its own tanks, hoses, and lines.

Answer

One system controlled by two separate brake pedals

Answer

Two brake systems that alternate every other stop

Answer

A single system with a backup compressor only

Question 6

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

Accepted Answer

The delay before the air reaches and works the brakes — Brake lag is the short delay while the air travels through the lines to the brakes after you push the pedal; unlike instant-acting hydraulic brakes, air brakes take about half a second or more to take hold.

Answer

The time the compressor needs to refill the tanks

Answer

The wait for the spring brakes to release

Answer

The pause between draining two air tanks

Speed & Space Management

Study questions with answers

1. On a dual air system, the low air warning should come on before pressure drops below 55 psi in which system?

2. Before driving a vehicle with a dual air system, how much pressure should you let build up in both the primary and secondary systems?

3. For a vehicle with air brakes, total stopping distance is made up of which four parts?

4. If one half of a dual air system loses most of its pressure, what should you expect?

5. What best describes a dual air brake system?

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

More CDL — Air Brakes topics

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