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. Counting perception, reaction, brake lag, and braking, an air brake vehicle's total stopping distance at 55 mph on dry pavement is about how much?

   Correct answer: Over 450 feet.

   Air brake lag adds roughly 32 feet at 55 mph, and combined with perception, reaction and braking distance the total comes to over 450 feet for an average driver in good conditions.

   Source: Section 5.4.4 - Stopping Distance

2. 2. How do air brakes differ from hydraulic brakes in how quickly they respond?

   Correct answer: Air brakes add a short lag, about a half second or more, for air to reach the brakes.

   Hydraulic brakes act instantly, but air brakes have brake lag, roughly a half second or more for air to flow through the lines, which adds distance to the total stop.

   Source: Section 5.4.4 - Stopping Distance (brake lag)

3. 3. In a dual air system running at operating rpm, how long should it take pressure to climb from 85 to 100 psi?

   Correct answer: 45 seconds.

   At operating rpm a dual system should reach 100 psi from 85 in no more than 45 seconds; building slower than that can let pressure fall too low on the road.

   Source: Section 5.3.3 - Final Air Brake Check (buildup rate)

4. 4. Using the recommended braking technique on a long downgrade, once you are in the proper low gear you should do what?

   Correct answer: Brake firmly to slow about 5 mph below your safe speed, release, then repeat as needed.

   In the proper low gear, brake hard enough for a definite slowdown to about 5 mph under your safe speed (roughly a three-second application), release, and repeat each time you climb back to your safe speed.

   Source: Section 5.4.6 - Proper Braking Technique