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. Compared with a car's hydraulic brakes, how quickly do air brakes respond?

   Correct answer: A little slower, since the air must travel through the lines

   Hydraulic brakes act instantly, while air brakes have a short lag as the air travels out to each brake.

   Source: 5.4.4 Stopping Distance

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

   Correct answer: About 32 feet

   According to the manual, that lag tacks on roughly 32 feet of travel at 55 mph on dry roads.

   Source: 5.4.4 Stopping Distance

3. 3. Total stopping distance with air brakes is made up of how many separate factors?

   Correct answer: Four

   The four pieces are perception distance, reaction distance, the brake lag distance, and braking distance.

   Source: 5.4.4 Stopping Distance

4. 4. For an average driver at 55 mph in good conditions, an air-brake vehicle's total stopping distance is about what?

   Correct answer: More than 450 feet

   The four parts add up to more than 450 feet at 55 mph for a typical driver in good conditions.

   Source: 5.4.4 Stopping Distance

5. 5. About how long does the air take to reach the brakes after you press the pedal?

   Correct answer: A half second or more

   A car's hydraulic brakes react instantly, but air needs about a half second or longer to reach the brakes.

   Source: 5.4.4 Stopping Distance

6. 6. What does 'brake lag' mean in an air-brake system?

   Correct answer: The delay before the brakes act after the pedal is pushed

   Brake lag is the short delay while air travels through the lines before the brakes actually take hold.

   Source: 5.4.4 Stopping Distance

7. 7. In a dual air system, what happens if one of the two systems loses most of its pressure?

   Correct answer: It takes longer to stop because some brakes aren't fully working

   With one system low, either the front or rear brakes won't work fully, so the vehicle needs more distance to stop.

   Source: 5.2 Dual Air Brake