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. At what speed can hydroplaning begin when a lot of water is on the road?

   Correct answer: As low as 30 mph

   Hydroplaning can start at speeds as low as 30 mph when there is enough water on the road.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

2. 2. Compared with a loaded cargo van, how does an empty one affect overhead clearance?

   Correct answer: An unloaded van rides taller than one that is loaded

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

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Managing Space)

3. 3. If your vehicle begins to hydroplane, what should you do?

   Correct answer: Release the accelerator and push in the clutch

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

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

4. 4. Why shouldn't you assume the height posted at a bridge or overpass is accurate?

   Correct answer: Repaving or packed snow may have lowered the actual clearance

   Repaving or packed snow may have reduced the clearance since the height was posted, so posted numbers can't be fully trusted.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Managing Space)

5. 5. Can a truck with a high center of gravity roll over at the posted speed for a curve?

   Correct answer: Yes, a high center of gravity can roll it over at the posted speed

   Testing has demonstrated that a tall, top-heavy load may flip a truck even at a curve's posted limit, so ease down to a safe speed first.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

6. 6. Why do empty trucks generally need a longer stopping distance than loaded ones?

   Correct answer: An empty truck has less traction and needs more distance to stop

   An empty truck has less traction, so it actually requires a greater stopping distance than a fully loaded one.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

7. 7. Why is it dangerous to brake while going through a curve?

   Correct answer: It can lock the wheels and cause a skid

   Braking in a curve makes it easier to lock the wheels and skid, so slow down before the curve instead.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

8. 8. When must you add a second to your following-distance count?

   Correct answer: At speeds over 40 mph

   At speeds over 40 mph you must add one second to the length-based following distance for safety.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Managing Space)

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

   Correct answer: By about one-third

   Wet roads can double stopping distance, so reduce your speed by about one-third, for example from 55 to around 35 mph.

   Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

10. 10. Below 40 mph, how much following distance does the manual suggest for vehicle length?

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

    The guideline gives one second of space for every 10 feet of length while you are under 40 mph.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Managing Space)

11. 11. On packed snow, how much should you cut your speed compared with dry pavement?

    Correct answer: By about a half or more

    On packed snow reduce your speed by a half or more, and on ice slow to a crawl.

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)

12. 12. What three distances add together to make up total stopping distance?

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

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

    Source: Tennessee CDL Manual — Section 2: Driving Safely (Controlling Speed)