Speed & Space Management

Study questions with answers

12 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. What is one good rule for following distance at speeds below 40 mph?

   Correct answer: One second for every 10 feet of vehicle length

   Allow at least one second of following distance for every 10 feet of vehicle length at speeds under 40 mph.

   Source: Louisiana CDL Manual, Section 2.7.1 (Space Ahead)

2. 2. At night, when you must use low beams, how should you adjust your speed?

   Correct answer: Slow down so you can stop within the distance you can see

   Because low beams reveal less of the roadway, reduce speed so you are able to halt within the range you can actually see.

   Source: Louisiana CDL Manual, Section 2.6.4 (Speed and Distance Ahead)

3. 3. By about how much should you reduce your speed on a wet road?

   Correct answer: By about one-third

   On a wet road, cut your speed by roughly one-third, for example from 55 down to about 35 mph.

   Source: Louisiana CDL Manual, Section 2.6.2 (Matching Speed to the Road Surface)

4. 4. When your speed doubles from 20 mph to 40 mph, how much longer does your braking distance become?

   Correct answer: It becomes about four times longer

   Doubling your speed makes the braking distance about four times longer, and the impact four times greater.

   Source: Louisiana CDL Manual, Section 2.6.1 (The Effect of Speed on Stopping Distance)

5. 5. At about 55 mph on dry pavement, what is the minimum total stopping distance for a typical vehicle?

   Correct answer: About 419 feet

   At 55 mph the vehicle travels a minimum of about 419 feet before it can be brought to a complete stop.

   Source: Louisiana CDL Manual, Section 2.6.1 (Stopping Distance)

6. 6. Total stopping distance is made up of which three parts?

   Correct answer: Perception, reaction, and braking distance

   Total stopping distance combines perception distance, reaction distance, and braking distance.

   Source: Louisiana CDL Manual, Section 2.6.1 (Stopping Distance)

7. 7. How does the height of an empty cargo van compare with the same van when loaded?

   Correct answer: An empty van rides higher than one that is loaded

   An empty cargo van rides higher than a loaded one, so clearing a bridge when loaded does not guarantee you will clear it empty.

   Source: Louisiana CDL Manual, Section 2.7.4 (Space Overhead)

8. 8. If you triple your speed from 20 to 60 mph, how much greater is the braking distance?

   Correct answer: About nine times greater

   Tripling your speed makes both the impact and the braking distance about nine times greater.

   Source: Louisiana CDL Manual, Section 2.6.1 (The Effect of Speed on Stopping Distance)

9. 9. Within highway work zones, what is the leading cause of injuries and deaths?

   Correct answer: Speeding traffic

   Speeding traffic is the leading cause of injuries and deaths in work zones, so obey posted work-zone limits.

   Source: Louisiana CDL Manual, Section 2.6.7 (Roadway Work Zones)

10. 10. How do you adjust your following distance for speeds above 40 mph?

    Correct answer: Add one more second

    When you go faster than 40 mph, add one more second to the following distance you calculated by length.

    Source: Louisiana CDL Manual, Section 2.7.1 (Space Ahead)

11. 11. On a downgrade, what should be your main way of controlling speed?

    Correct answer: The engine's braking effect in a low gear

    Use the braking effect of the engine in a low gear as your principal way of holding speed down on a grade, saving the brakes for when needed.

    Source: Louisiana CDL Manual, Section 2.6.6 (Speed on Downgrades)

12. 12. Hydroplaning can begin at speeds as low as what, when a lot of water is on the road?

    Correct answer: 30 mph

    When a lot of water is standing on the road, hydroplaning may begin at speeds as low as 30 mph.

    Source: Louisiana CDL Manual, Section 2.6.2 (Hydroplaning)