Speed & Space Management

Study questions with answers

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

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

   On a long or steep downgrade the brakes are only a supplement to the braking effect of the engine, which does most of the work in a low gear.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.6 - Proper Braking Technique

2. 2. Compared with hydraulic brakes, air brakes add an extra delay called brake lag. Why does it happen?

   Correct answer: It takes time for the air to travel through the lines to the brakes

   Hydraulic brakes act instantly, but air needs a little time (a half second or more) to travel through the lines to the brakes, adding brake lag.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.4 - Stopping Distance

3. 3. What happens as the brake shoes and linings press against the drum to slow the vehicle?

   Correct answer: Friction slows the vehicle and produces heat

   Pressing the linings against the drum produces friction that slows the vehicle, and that friction also generates a lot of heat.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.8 - Foundation Brakes

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

   Correct answer: It will take longer to stop, so stop safely and get it fixed

   Losing one half means either the front or rear brakes will not work fully, so it takes longer to stop; bring the vehicle to a safe stop and have it repaired.

   Source: Minnesota Commercial Driver's License Manual, Section 5.2 - Dual Air Brake

5. 5. Using proper downgrade braking, once you are in a low gear, when do you release the brakes after applying them?

   Correct answer: After your speed drops to about five mph below your safe speed

   Apply firmly enough to feel a definite slowdown, then release once your speed has dropped to about five mph below your safe speed, and repeat as needed.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.6 - Proper Braking Technique

6. 6. The total stopping distance for an air brake vehicle is made up of which four parts?

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

   For air brakes the total is perception distance plus reaction distance plus brake lag distance plus braking distance.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.4 - Stopping Distance