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

   Correct answer: About 32 feet

   The manual states that the brake lag distance at 55 mph on dry pavement adds about 32 feet.

   Source: Section 5.4.4 - Stopping Distance

2. 2. Before driving a vehicle with a dual air system, what minimum pressure should build in both the primary and secondary systems?

   Correct answer: 100 psi

   Give the compressor time to build at least 100 psi in both the primary and secondary systems before you start driving.

   Source: Section 5.2 - Dual Air Brake

3. 3. For an average driver at 55 mph in good conditions, the total stopping distance of an air brake vehicle is about how far?

   Correct answer: More than 450 feet

   Adding all four factors together, the total stopping distance at 55 mph for an average driver with good traction and brakes works out to more than 450 feet.

   Source: Section 5.4.4 - Stopping Distance

4. 4. What does 'brake lag' refer to in an air brake system?

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

   Brake lag is the short delay, unique to air brakes, between pressing the pedal and the brakes actually taking hold, because the air has to travel through the lines first.

   Source: Section 5.4.4 - Stopping Distance

5. 5. 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

   Because of brake lag, an air brake vehicle's total stopping distance adds together the perception, reaction, brake lag, and braking distances.

   Source: Section 5.4.4 - Stopping Distance

6. 6. In a dual air brake system, what happens to stopping ability if one of the two systems is very low on pressure?

   Correct answer: Either the front or rear brakes won't work fully, so stopping takes longer

   If one circuit of a dual system runs very low, either the front or the rear brakes won't be fully operating, which makes the vehicle take longer to stop.

   Source: Section 5.2 - Dual Air Brake

7. 7. Compared with the instant action of hydraulic brakes, how long does air take to reach the brakes after the pedal is pushed?

   Correct answer: About one half second or more

   Hydraulic brakes respond instantly, but with air brakes it takes roughly half a second or longer for the air to flow through the lines to the brakes.

   Source: Section 5.4.4 - Stopping Distance