South Dakota CDL — General Knowledge practice
South Dakota CDL — General Knowledge: Speed & Space Management practice test
Choosing a safe speed, keeping a space cushion, adjusting for weather and traffic, and understanding stopping distance.
Content reviewed against official driver handbooks · August 12, 2026
11 questions · pass with 9 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
11 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.
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1. What do wet roads do to stopping distance, according to the manual?
Correct answer: They can double it
A slippery road takes longer to stop on, and the manual says wet roads can double stopping distance. A driver has to go slower to stop in the same space as on a dry road.
Source: South Dakota Commercial Driver License Manual — Section 2.6.2, Matching Speed to the Road Surface
2. At 55 mph on dry pavement, which part of total stopping distance is the longest, by the manual's figures?
Correct answer: Braking distance, at about 216 feet
The manual's figures at 55 mph are 142 feet for perception, 61 feet for reaction, and about 216 feet for braking with good brakes on dry pavement. Braking is the largest share.
Source: South Dakota Commercial Driver License Manual — Section 2.6.1, Stopping Distance
3. In the manual's explanation of hydroplaning, what job do the grooves in a tire do?
Correct answer: They carry water away
Hydroplaning is more likely with low tire pressure or worn tread. The manual explains that the grooves carry the water away, and grooves that are not deep do not work well.
Source: South Dakota Commercial Driver License Manual — Section 2.6.2, Matching Speed to the Road Surface
4. A two-lane South Dakota highway is posted at 65 mph. A tow truck is stopped ahead with amber lights flashing, and no one is directing traffic. By the time you are 300 feet from it, what must your speed be?
Correct answer: 45 mph or less
On a two-lane highway the law requires slowing, at least 300 feet before the stopped vehicle, to a speed at least 20 mph below the posted limit. With a 65 mph limit, that means 45 mph or less, followed by proceeding with caution.
Source: South Dakota Commercial Driver License Manual — Attention notice, South Dakota Codified Law 32-31-6.1
5. A heavy vehicle's brakes, tires, springs, and shock absorbers are built to perform best under what condition?
Correct answer: With the vehicle fully loaded
A heavier vehicle makes its brakes work harder and absorb more heat, yet these parts are designed for a full load. That is why an empty truck, with less traction, needs more distance to stop.
Source: South Dakota Commercial Driver License Manual — Section 2.6.1, Stopping Distance
6. What does the manual give as the main reason drivers exceed speed limits?
Correct answer: To save time
Saving time is named as the main reason for speeding. The manual answers that anyone trying to go faster than the traffic around them will not save much, and that the risks are not worth it.
Source: South Dakota Commercial Driver License Manual — Section 2.6.5, Speed and Traffic Flow
7. Which part of total stopping distance covers the time between your eyes seeing a hazard and your brain recognizing it?
Correct answer: Perception distance
Perception distance is how far the vehicle travels from the moment the eyes see a hazard until the brain recognizes it. Reaction distance comes next, before the driver physically gets on the brakes.
Source: South Dakota Commercial Driver License Manual — Section 2.6.1, Stopping Distance
8. The posted limit on a South Dakota two-lane road is 20 mph, and a stopped vehicle ahead is using yellow warning lights. To what speed must you slow?
Correct answer: 5 mph
The 20-mph-under rule cannot work where the limit is already low. When the limit is posted at 20 mph or less, the law sets the passing speed at 5 mph.
Source: South Dakota Commercial Driver License Manual — Attention notice, South Dakota Codified Law 32-31-6.1
9. Under ideal conditions, what is the least total distance a vehicle going 55 mph covers before it can be stopped completely?
Correct answer: 419 feet
Adding perception, reaction, and braking distance gives a total of at least 419 feet at 55 mph, even with everything in the driver's favor.
Source: South Dakota Commercial Driver License Manual — Section 2.6.1, Stopping Distance
10. You are driving 55 mph on a dry highway when steady rain wets the road. About what speed does the manual's wet-road rule suggest?
Correct answer: About 35 mph
On a wet road the manual says to cut speed by roughly one-third. Its own example is slowing from 55 mph to about 35 mph.
Source: South Dakota Commercial Driver License Manual — Section 2.6.2, Matching Speed to the Road Surface
11. About how far ahead can you see with low-beam headlights at night, compared with high beams?
Correct answer: About 250 feet with low beams and about 350 to 500 feet with high beams
Low beams light roughly 250 feet of road and high beams roughly 350 to 500 feet. Speed has to be held low enough to stop inside the range of the headlights.
Source: South Dakota Commercial Driver License Manual — Section 2.11.4, Vehicle Factors
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Every South Dakota question is written from the official South Dakota driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free