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

   Correct answer: It becomes about four times as long

   Doubling speed from 20 to 40 mph makes the braking distance about four times longer, and the impact four times greater.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (The Effect of Speed on Stopping Distance)

2. 2. On packed snow, by about how much should a driver cut speed?

   Correct answer: By about a half or more

   On packed snow you should reduce speed by a half or more, and on ice slow to a crawl and stop as soon as it is safe.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Matching Speed to the Road Surface)

3. 3. When should a driver downshift to a lower gear on a manual-transmission truck relative to a steep hill?

   Correct answer: Before starting down the grade

   Downshift before starting down the hill; do not try to downshift after your speed has already built up, because you may not be able to get into a lower gear.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Select the Right Gear before Starting Down the Grade)

4. 4. Why do empty trucks generally require greater stopping distances than loaded ones?

   Correct answer: Because an empty vehicle has less traction

   An empty vehicle has less traction, so even though its brakes work best when loaded, an empty truck needs more distance to stop.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (The Effect of Vehicle Weight on Stopping Distance)

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

   Correct answer: By about one-third

   Wet roads can double stopping distance, so reduce your speed by about one-third, such as slowing from 55 to about 35 mph.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Matching Speed to the Road Surface)

6. 6. What two things can happen if you take a curve too fast in a loaded commercial vehicle?

   Correct answer: The vehicle may skid off the road or roll over

   Taking a curve too fast can cause the tires to lose traction and skid off the road, or the vehicle can keep traction and roll over.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Speed and Curves)

7. 7. How does the space under a vehicle behave when it is heavily loaded?

   Correct answer: The clearance can become very small

   The clearance below a vehicle can become very small when heavily loaded, which is a problem on dirt roads, unpaved yards, drainage channels, and railroad tracks.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Space Below)

8. 8. Driving a 40-foot vehicle at speeds over 40 mph, how many seconds of following distance should you keep?

   Correct answer: 5 seconds

   A 40-foot vehicle needs 4 seconds below 40 mph, plus one more second above 40 mph, for a total of 5 seconds.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (How Much Space?)

9. 9. What is a sign of standing water that could cause hydroplaning?

   Correct answer: Clear reflections and tire splashes on the road

   Clear reflections, tire splashes, and raindrops on the road surface are indications of standing water where hydroplaning can occur.

   Source: Minnesota CDL Manual — Section 2: Driving Safely (Hydroplaning)

10. 10. On downgrades, what is the principal way a driver should control the vehicle's speed?

    Correct answer: Using the braking effect of the engine

    You must use the braking effect of the engine as the principal way to control speed on downgrades, saving your brakes for when you need them.

    Source: Minnesota CDL Manual — Section 2: Driving Safely (Speed on Downgrades)

11. 11. 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: Minnesota CDL Manual — Section 2: Driving Safely (Stopping Distance)

12. 12. How much following distance does the manual recommend for speeds below 40 mph?

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

    Keep at least one second for each 10 feet of vehicle length at speeds below 40 mph, and add one second above 40 mph.

    Source: Minnesota CDL Manual — Section 2: Driving Safely (How Much Space?)