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. Going from 20 mph up to 40 mph roughly multiplies your braking distance by how much?

   Correct answer: About 4 times greater

   Doubling speed from 20 to 40 mph makes the braking distance (and impact force) about four times greater.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.1)

2. 2. You are behind the wheel of a 40-foot vehicle traveling 35 mph. What following distance, in seconds, should you maintain?

   Correct answer: 4 seconds

   Below 40 mph you allow one second for each 10 feet, so a 40-foot vehicle needs about 4 seconds of following distance.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.7.1)

3. 3. Why is the space directly ahead of your vehicle the most important space to manage?

   Correct answer: Because the vehicle ahead is the one you most often run into

   The vehicle trucks and buses most often hit is the one ahead of them, usually from following too closely, so the space ahead is the most important to protect.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.7.1)

4. 4. Which factors determine a safe speed for descending a long, steep grade?

   Correct answer: Total weight, grade length and steepness, road conditions, and weather

   A safe downgrade speed depends on the total weight of vehicle and cargo, the length and steepness of the grade, road conditions, and the weather.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.16.1)

5. 5. If your drive wheels start to hydroplane, what should you do?

   Correct answer: Release the accelerator and push in the clutch

   When hydroplaning, release the accelerator and push in the clutch to let the wheels turn freely and slow down; do not use the brakes.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.2)

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

   Correct answer: As low as 30 mph

   Hydroplaning can start at speeds as low as 30 mph when enough water is present, and it is more likely with low tire pressure or worn tread.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.2)

7. 7. How does wet pavement affect your stopping distance?

   Correct answer: It can double your stopping distance

   Wet pavement can double how far it takes to stop, so you must slow down to keep your stopping distance close to what it would be on a dry road.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.2)

8. 8. The manual suggests reducing your speed by about how much on a wet road?

   Correct answer: By about one-third

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

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.2)

9. 9. On packed snow, by about how much should you reduce your speed?

   Correct answer: By about half or more

   On packed snow you should cut your speed by about half or more; on ice you should slow to a crawl and stop as soon as you safely can.

   Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.6.2)

10. 10. Why should you avoid traveling alongside other vehicles on a multi-lane road?

    Correct answer: You may be trapped or another driver may turn into you

    Driving next to another vehicle risks being trapped with nowhere to go if you must change lanes, or being hit if that driver suddenly moves into your lane.

    Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.7.3)

11. 11. When approaching an off-ramp or on-ramp, why should you be cautious about the posted speed?

    Correct answer: The posted speed may be safe for cars but too fast for a heavy vehicle

    Ramp speed signs are often set for cars; those speeds may be too fast for a larger or loaded commercial vehicle, especially on ramps that curve and drop at once.

    Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.8.2)

12. 12. The manual's rule for following distance at speeds under 40 mph is about one second for each what?

    Correct answer: Each 10 feet of vehicle length

    Below 40 mph, allow at least one second of following distance for every 10 feet of vehicle length; above 40 mph add one more second.

    Source: North Carolina CDL Driver Handbook — Section 2: Driving Safely (2.7.1)