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. How much can a wet road increase your stopping distance?

   Correct answer: It can double the stopping distance

   Wet roads can double your stopping distance, so you must slow down to be able to stop in the same distance as on dry pavement.

   Source: Indiana CDL Manual, Section 2 (Matching Speed to the Road Surface)

2. 2. On packed snow, how much should you reduce your speed compared with dry conditions?

   Correct answer: By a half or more

   Reduce your speed by a half or more on packed snow, and on ice slow to a crawl and stop as soon as you safely can.

   Source: Indiana CDL Manual, Section 2 (Matching Speed to the Road Surface)

3. 3. Which three distances add together to make up total stopping distance?

   Correct answer: Perception, reaction, and braking distance

   Total stopping distance is the sum of perception distance, reaction distance, and braking distance.

   Source: Indiana CDL Manual, Section 2 (Stopping Distance)

4. 4. What is 'black ice' and why is it dangerous?

   Correct answer: A thin clear layer that makes the road look only wet

   Black ice is a thin, clear layer through which the road shows, making the surface look merely wet while it is actually icy.

   Source: Indiana CDL Manual, Section 2 (Identifying Slippery Surfaces)

5. 5. Why is an empty cargo van a concern for overhead clearance?

   Correct answer: An empty van sits higher than a loaded one

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

   Source: Indiana CDL Manual, Section 2 (Space Overhead)

6. 6. What is the recommended following distance for a 40-foot vehicle traveling below 40 mph?

   Correct answer: 4 seconds

   Allow one second for each 10 feet of vehicle length below 40 mph, so a 40-foot vehicle needs about 4 seconds.

   Source: Indiana CDL Manual, Section 2 (Space Ahead)

7. 7. Why do empty trucks often require a longer stopping distance than loaded ones?

   Correct answer: An empty vehicle has less traction

   An empty vehicle has less traction, and the brakes, tires, and suspension are designed to work best when the vehicle is fully loaded.

   Source: Indiana CDL Manual, Section 2 (Effect of Vehicle Weight on Stopping Distance)

8. 8. If you double your speed from 20 to 40 mph, how does your braking distance change?

   Correct answer: It becomes about four times longer

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

   Source: Indiana CDL Manual, Section 2 (Effect of Speed on Stopping Distance)

9. 9. Why must you use the braking effect of the engine as your main way of controlling speed on a long downgrade?

   Correct answer: It saves the brakes from overheating and fading

   Relying on engine braking saves your service brakes so they do not overheat and fade; shift to a low gear before starting down.

   Source: Indiana CDL Manual, Section 2 (Speed on Downgrades)

10. 10. If your vehicle begins to hydroplane, what is the correct response?

    Correct answer: Release the accelerator and push in the clutch

    Release the accelerator and push in the clutch to let the wheels slow and turn freely; do not use the brakes to slow down.

    Source: Indiana CDL Manual, Section 2 (Hydroplaning)

11. 11. On a wet road, about how much should you reduce your speed?

    Correct answer: By about one-third

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

    Source: Indiana CDL Manual, Section 2 (Matching Speed to the Road Surface)

12. 12. Above 40 mph, how do you adjust the following-distance rule of one second per 10 feet of length?

    Correct answer: Add one second

    At speeds over 40 mph you must add one more second for safety, so a 40-foot vehicle needs 5 seconds instead of 4.

    Source: Indiana CDL Manual, Section 2 (Space Ahead)