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

   Correct answer: Perception, reaction, and braking distance

   Total stopping distance is perception distance plus reaction distance plus braking distance.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Stopping Distance)

2. 2. How can a wet road affect your stopping distance?

   Correct answer: It can double the stopping distance

   A wet surface can lengthen your stopping distance to twice normal, so you must ease off to halt within the same room a dry road allows.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Slippery Surfaces)

3. 3. Traveling near 55 mph on a dry road surface with brakes in good shape, about what is the least total distance a heavy vehicle needs to stop?

   Correct answer: About 419 feet

   At 55 mph the vehicle travels a minimum of about 419 feet before stopping when perception, reaction, and braking are added together.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Stopping Distance)

4. 4. In highway work zones, what is the leading cause of injuries and fatalities?

   Correct answer: Speeding traffic

   Speeding traffic is the leading cause of injury and death in work zones, so obey the posted limits throughout.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Roadway Work Zones)

5. 5. What is black ice, and why is it dangerous?

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

   Black ice is a thin, clear layer that makes the road look merely wet, so watch for it whenever temperatures are below freezing and the road looks wet.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Black Ice)

6. 6. What is the safest way to handle a curve in a heavy vehicle?

   Correct answer: Slow down before entering the curve

   Slow to a safe speed before entering the curve, because braking within a curve makes it easier to lock the wheels and skid.

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

7. 7. In heavy traffic, what is usually the safest speed to travel?

   Correct answer: The speed of the surrounding traffic

   The safest speed in heavy traffic is generally the speed of the other vehicles, since traffic moving together is less likely to collide.

   Source: South Carolina CDL Manual — Section 2: Driving Safely (Speed and Traffic Flow)

8. 8. What should be your main way of controlling speed when descending a long, steep grade?

   Correct answer: The braking effect of the engine

   Use the engine's braking effect as the principal means of controlling speed on a downgrade, saving the brakes for when they are needed.

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

9. 9. Why does an empty truck often need a longer stopping distance than a loaded one?

   Correct answer: An empty vehicle has less traction

   An empty vehicle has less traction, so its brakes, tires, and suspension work best when loaded and it may take longer to stop empty.

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

10. 10. If you double your speed, roughly how much longer does your braking distance become?

    Correct answer: About four times as long

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

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

11. 11. Within what distance should a driver always be capable of coming to a stop?

    Correct answer: The distance you can see ahead

    A driver must always be able to halt inside the range that is visible ahead, cutting speed when fog, rain, or night narrows that range.

    Source: South Carolina CDL Manual — Section 2: Driving Safely (Speed and Distance Ahead)

12. 12. By about how much should you cut your speed on a wet road?

    Correct answer: By about one-third

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

    Source: South Carolina CDL Manual — Section 2: Driving Safely (Slippery Surfaces)