Speed & Space Management

Study questions with answers

7 sample Speed & Space Management questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. In a dual air system at operating rpm, air pressure should climb from 85 to 100 psi in what amount of time?

   Correct answer: Within 45 seconds

   With the engine at operating speed, a dual air system should raise pressure from 85 to 100 psi in 45 seconds; larger-than-minimum tanks may take a bit longer.

   Source: Connecticut CDL Manual, Section 5.3.3 (Final Air Brake Check)

2. 2. For an average driver at 55 mph in good conditions, the total stopping distance of an air brake vehicle is about how far?

   Correct answer: Over 450 feet

   Adding perception, reaction, brake lag, and braking distance, the total at 55 mph comes to more than 450 feet for an average driver in good traction and brake conditions.

   Source: Connecticut CDL Manual, Section 5.4.4 (Stopping Distance)

3. 3. In a dual air brake system, what happens if one of the two systems becomes very low on pressure?

   Correct answer: One end of the rig, front or rear, loses full braking power, so stops take longer

   With one circuit very low, either the front or rear brakes lose full function, which lengthens your stopping distance; stop safely and get it repaired.

   Source: Connecticut CDL Manual, Section 5.2 (Dual Air Brake)

4. 4. At 55 mph on dry pavement, roughly how much distance does air brake lag add?

   Correct answer: About 32 feet

   The lag of an air brake system adds roughly 32 feet of travel at 55 mph on dry pavement, on top of the other stopping-distance factors.

   Source: Connecticut CDL Manual, Section 5.4.4 (Stopping Distance)

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

   Correct answer: The short time it takes air to reach the brakes after the pedal is pressed

   Because air must travel through the lines, there is about a half second or more of delay before air brakes react, unlike hydraulic brakes that act instantly.

   Source: Connecticut CDL Manual, Section 5.4.4 (Stopping Distance)

6. 6. On a long, steep downgrade, how should the service brakes be used?

   Correct answer: Only to supplement the braking effect of the engine

   The brakes on a long or steep downgrade are just a supplement to engine braking; get into a low gear first, then use light, timed brake applications.

   Source: Connecticut CDL Manual, Section 5.4.6 (Proper Braking Technique)

7. 7. Total stopping distance for an air brake vehicle is made up of which factors?

   Correct answer: Perception, reaction, brake lag, and braking distance

   Air brakes add a lag component, so total stopping distance combines perception distance, reaction distance, brake lag distance, and braking distance.

   Source: Connecticut CDL Manual, Section 5.4.4 (Stopping Distance)