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. By about how much should you reduce speed on a wet road?

   Correct answer: By about one third

   Cut your speed by roughly one third on wet pavement, for example from 55 down to about 35 mph.

   Source: Wisconsin CDL Manual, Section 2.6.2 — Matching Speed to the Road Surface

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

   Correct answer: It roughly quadruples

   Doubling the speed roughly quadruples the braking distance and the impact force.

   Source: Wisconsin CDL Manual, Section 2.6.1 — The Effect of Speed on Stopping Distance

3. 3. At what speed can hydroplaning begin if there is enough water on the road?

   Correct answer: As low as 30 mph

   With a lot of water present, hydroplaning can start at speeds as low as 30 mph.

   Source: Wisconsin CDL Manual, Section 2.6.2 — Matching Speed to the Road Surface

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

   Correct answer: Perception, reaction and braking distance

   It is the sum of perception distance, reaction distance and braking distance.

   Source: Wisconsin CDL Manual, Section 2.6.1 — Stopping Distance

5. 5. What two things can happen if you take a curve too fast in a large vehicle?

   Correct answer: You skid off the road or roll over

   The tires can lose traction and slide straight off the road, or they can hold and the vehicle rolls over.

   Source: Wisconsin CDL Manual, Section 2.6.3 — Speed and Curves

6. 6. Below 40 mph, how much following distance in seconds does a 40-foot vehicle need?

   Correct answer: Four seconds

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

   Source: Wisconsin CDL Manual, Section 2.7.1 — Space Ahead

7. 7. Strong winds tend to cause the most trouble staying in your lane for which vehicles?

   Correct answer: Lighter vehicles

   Lighter vehicles are usually affected more, and the trouble can be strongest as you emerge from a tunnel.

   Source: Wisconsin CDL Manual, Section 2.7.3 — Space to the Sides

8. 8. Regarding overhead clearance, how does an empty cargo van compare with a loaded one?

   Correct answer: An empty van rides higher than a loaded one

   An empty van rides higher than a loaded one, so clearing a bridge loaded does not guarantee you will clear it empty.

   Source: Wisconsin CDL Manual, Section 2.7.4 — Space Overhead

9. 9. What should be your principal method of controlling speed on a long downgrade?

   Correct answer: The engine's braking effect

   Rely on engine braking as your chief means of holding speed down, and save the service brakes for when they are truly needed.

   Source: Wisconsin CDL Manual, Section 2.6.6 — Speed on Downgrades

10. 10. When should you shift into a low gear for a downgrade?

    Correct answer: Before you start down the grade

    Move the transmission into a low gear before you start down the grade, then use proper braking technique.

    Source: Wisconsin CDL Manual, Section 2.6.6 — Speed on Downgrades

11. 11. How does the following-distance rule change once you are traveling faster than 40 mph?

    Correct answer: Add one second for safety

    Above 40 mph you add one extra second to the figure you get from the one-second-per-10-feet rule.

    Source: Wisconsin CDL Manual, Section 2.7.1 — Space Ahead

12. 12. At speeds below 40 mph, how much following distance does the manual's rule call for?

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

    Allow at least one second of space for every 10 feet of vehicle length when traveling under 40 mph.

    Source: Wisconsin CDL Manual, Section 2.7.1 — Space Ahead