Speed & Space Management

Study questions with answers

5 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. You find you must keep increasing application pressure to hold a steady speed. What does this most likely indicate?

   Correct answer: The brakes are fading

   Needing more and more application pressure to keep the same speed is a sign of fading brakes; slow down and shift to a lower gear.

   Source: Illinois CDL Study Guide — Section 5.1.10: Application Pressure Gauge

2. 2. If one half of a dual air brake system loses most of its pressure, what is the result?

   Correct answer: Either the front or rear brakes work only partly, so it takes longer to stop

   With one circuit low, only the front or only the rear brakes work fully, increasing stopping distance; stop safely and have it fixed.

   Source: Illinois CDL Study Guide — Section 5.2: Dual Air Brake

3. 3. What added delay do air brakes introduce that hydraulic brakes on a car do not?

   Correct answer: Brake lag, the time for air to travel through the lines

   Air takes about half a second or more to reach the brakes, adding brake-lag distance that instant-acting hydraulic brakes do not have.

   Source: Illinois CDL Study Guide — Section 5.4.4: Stopping Distance

4. 4. Using the recommended downgrade braking method in the proper low gear, when do you release the brakes?

   Correct answer: Once your speed is about 5 mph below your chosen safe speed

   Apply firmly until you slow to roughly 5 mph under your chosen safe speed, then release for a few seconds; repeat as speed builds back up. Braking only supplements engine braking on a downgrade.

   Source: Illinois CDL Study Guide — Section 5.4.6: Proper Braking Technique

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

   Correct answer: About 32 feet

   Air brake lag adds about 32 feet of stopping distance at 55 mph on dry roads, part of a total stopping distance of over 450 feet.

   Source: Illinois CDL Study Guide — Section 5.4.4: Stopping Distance