Speed & Space Management

Study questions with answers

4 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. At 55 mph on dry pavement, about how many feet does air brake lag add to the stopping distance?

   Correct answer: About 32 feet

   Brake lag alone contributes roughly 32 feet at 55 mph on dry pavement, which helps push the total stopping distance to over 450 feet.

   Source: Section 5.4.4 - Stopping Distance

2. 2. On a long, steep downgrade, the service brakes should be used in what role?

   Correct answer: As a supplement to the engine's braking effect

   On a long or steep grade the brakes only supplement engine braking; get into a low gear first, then use the brakes in short applications.

   Source: Section 5.4.6 - Proper Braking Technique

3. 3. Which four elements add up to the total stopping distance for an air brake vehicle?

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

   For air brakes the total is the sum of perception distance, reaction distance, the added brake lag distance, and the actual braking distance.

   Source: Section 5.4.4 - Stopping Distance

4. 4. What is "brake lag" in an air brake system?

   Correct answer: The short delay while air travels to the brakes after you press the pedal

   Unlike hydraulic brakes, air brakes need a moment, about half a second or more, for air to travel through the lines, adding a delay before braking begins.

   Source: Section 5.4.4 - Stopping Distance