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. Above 40 mph, how does the following-distance rule change for that same 60-foot rig?

   Correct answer: It rises to about 7 seconds

   Above 40 mph you add one second, so a 60-foot vehicle would need about 7 seconds of following distance.

   Source: Colorado CDL Manual, Section 2.7.1 (Space Ahead)

2. 2. Hydroplaning can begin at speeds as low as what, when there is a lot of water on the road?

   Correct answer: As low as 30 mph

   Given enough standing water, a vehicle can begin to hydroplane at just 30 mph, and the risk rises when tires are underinflated or their tread is worn down.

   Source: Colorado CDL Manual, Section 2.6.2 (Matching Speed to the Road Surface)

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

   Correct answer: The same speed as the surrounding traffic

   The safest speed in heavy traffic is the speed of the other vehicles, since vehicles moving the same direction at the same speed rarely collide.

   Source: Colorado CDL Manual, Section 2.6.5 (Speed and Traffic Flow)

4. 4. Testing has shown that a truck carrying a tall center of gravity may tip over on a curve at which speed?

   Correct answer: Even at the posted speed limit for the curve

   A truck with a tall center of gravity can flip on a curve even when traveling at the curve's posted limit, so ease down to a safe speed before you enter it.

   Source: Colorado CDL Manual, Section 2.6.3 (Speed and Curves)

5. 5. Why does an empty truck generally need a longer stopping distance than a loaded one?

   Correct answer: Because an empty truck has less traction

   A vehicle's brakes, tires, and springs perform best under a full load; when a truck runs empty it grips the road less and takes longer to halt.

   Source: Colorado CDL Manual, Section 2.6.1 (Stopping Distance)

6. 6. What is 'black ice'?

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

   Black ice is a thin, clear layer of ice you can see the road through, which makes the pavement merely look wet.

   Source: Colorado CDL Manual, Section 2.6.2 (Matching Speed to the Road Surface)

7. 7. At a speed under 40 mph in a 60-foot rig, how many seconds of space should you leave ahead?

   Correct answer: About 6 seconds

   At one second per 10 feet of length, a 60-foot vehicle under 40 mph needs about 6 seconds of following distance.

   Source: Colorado CDL Manual, Section 2.7.1 (Space Ahead)

8. 8. How much can a wet road increase your stopping distance, and how should you adjust speed?

   Correct answer: It can double stopping distance, so slow by about one-third

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

   Source: Colorado CDL Manual, Section 2.6.2 (Matching Speed to the Road Surface)

9. 9. Within highway work zones, which factor is the leading cause of injuries and deaths?

   Correct answer: Speeding traffic

   Traffic moving too fast is the top source of injuries and fatalities in work zones, so always honor the posted limits there.

   Source: Colorado CDL Manual, Section 2.6.7 (Roadway Work Zones)

10. 10. On packed snow, by about how much should a driver reduce speed?

    Correct answer: By about a half or more

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

    Source: Colorado CDL Manual, Section 2.6.2 (Matching Speed to the Road Surface)

11. 11. If your speed rises from 20 mph up to 40 mph, what happens to the braking distance?

    Correct answer: It becomes about four times as long

    Doubling your speed makes the impact about four times greater and the braking distance about four times longer.

    Source: Colorado CDL Manual, Section 2.6.1 (Stopping Distance)

12. 12. Why is checking overhead clearance important even when a bridge posts a height?

    Correct answer: Because repaving or snow may have lowered the real clearance

    Repaving or packed snow may have reduced clearance since the height was posted, and an empty van rides higher than a loaded one, so do not simply trust the sign.

    Source: Colorado CDL Manual, Section 2.7.4 (Space Overhead)