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. Using the rule of one second per 10 feet of vehicle length, how many seconds of following distance should a 60-foot rig keep at speeds below 40 mph?

   Correct answer: About 6 seconds

   At speeds under 40 mph you allow one second for each 10 feet of length, so a 60-foot vehicle needs about 6 seconds of following distance.

   Source: New Jersey CDL Manual — Section 2: Driving Safely (Space Ahead)

2. 2. What 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: New Jersey CDL Manual — Section 2: Driving Safely (Stopping Distance)

3. 3. How far can you typically see ahead with low-beam headlights, and how does that affect your speed?

   Correct answer: About 250 feet, so slow down to stop within that distance

   Low beams light about 250 feet ahead, so you must slow enough to stop within that range; high beams reach roughly 350 to 500 feet.

   Source: New Jersey CDL Manual — Section 2: Driving Safely (Vehicle Factors)

4. 4. Why is speeding the number-one concern in roadway work zones?

   Correct answer: It is the top cause of injury and death in work zones

   Speeding traffic is the leading cause of injury and death in work zones, so you must obey the posted limits and slow further when workers are near.

   Source: New Jersey CDL Manual — Section 2: Driving Safely (Roadway Work Zones)

5. 5. How does the following-distance rule change once your speed rises above 40 mph?

   Correct answer: Add one second for safety

   Above 40 mph you add one second for safety, so a 40-foot vehicle that needs 4 seconds below 40 mph should keep 5 seconds at higher speeds.

   Source: New Jersey CDL Manual — Section 2: Driving Safely (Space Ahead)

6. 6. When speed rises from 20 mph up to 40 mph, how is your braking distance affected?

   Correct answer: It becomes about four times longer

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

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

7. 7. 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 happen at speeds as low as 30 mph when a lot of water is present, and it is more likely with low tire pressure or worn tread.

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

8. 8. Within what distance of an oncoming vehicle must you dim your high beams?

   Correct answer: Within 500 feet

   Lower your beams when an approaching vehicle is 500 feet away, and likewise when trailing another vehicle by 500 feet, to keep from creating glare.

   Source: New Jersey CDL Manual — Section 2: Driving Safely (Avoid Blinding Others)

9. 9. 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 turn freely and slow down; do not use the brakes, which can worsen the loss of control.

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

10. 10. Compared with a fully loaded truck, why does an empty truck often need a greater stopping distance?

    Correct answer: An empty truck has less traction and can need more room to stop

    Brakes and suspension perform best under a full load; with the truck empty there is less traction, so a longer distance may be needed to stop.

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

11. 11. In heavy traffic, what is generally the safest speed to travel?

    Correct answer: The speed of the surrounding traffic

    In dense traffic the safest pace matches the surrounding vehicles, because those moving one way at a shared speed rarely collide.

    Source: New Jersey CDL Manual — Section 2: Driving Safely (Speed and Traffic Flow)

12. 12. Traveling 55 mph on dry pavement with sound brakes, roughly how far does a vehicle move from spotting a hazard to a full stop?

    Correct answer: About 419 feet

    At 55 mph the total stopping distance is a minimum of about 419 feet, combining roughly 142 feet of perception, 61 feet of reaction, and 216 feet of braking.

    Source: New Jersey CDL Manual — Section 2: Driving Safely (Stopping Distance)