Arizona CDL — General Knowledge practice
Arizona 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
14 questions · pass with 11 correct. You get instant feedback and an explanation after every answer.
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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.
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1. How many seconds of following distance should a 40-foot vehicle keep at speeds over 40 mph?
Correct answer: 5 seconds
A 40-foot vehicle needs 4 seconds under 40 mph, plus one extra second above 40 mph, for a total of 5 seconds of following space.
Source: Arizona CDL Manual — Section 2: Driving Safely
2. On a wet road, by about how much should you cut your speed?
Correct answer: By about one-third
Wet pavement can double stopping distance, so slow by roughly a third — for example from 55 to about 35 mph — to keep a safe margin.
Source: Arizona CDL Manual — Section 2: Driving Safely
3. What must serve as your principal means of controlling speed on a long downgrade?
Correct answer: The braking effect of the engine
Engine braking is the main tool on downgrades — greatest near the governed rpm in a low gear — so the service brakes stay available for slowing or stopping when needed.
Source: Arizona CDL Manual — Section 2: Driving Safely
4. On dry pavement at 55 mph with good brakes, braking distance alone is about how far?
Correct answer: About 216 feet
The braking portion alone eats up roughly 216 feet at 55 mph on dry pavement, which is only part of the far larger total stopping distance.
Source: Arizona CDL Manual — Section 2: Driving Safely
5. At about 60 mph, your total stopping distance compares to what?
Correct answer: Longer than an entire football field
By 60 mph the distance needed to stop exceeds a football field's length, a stark reminder of how speed multiplies stopping needs.
Source: Arizona CDL Manual — Section 2: Driving Safely
6. Below 40 mph, how much following distance does the manual suggest per 10 feet of vehicle length?
Correct answer: One second
Allow about one second of space for each ten feet of your rig's length at speeds under 40 mph, then add one more second once you go faster.
Source: Arizona CDL Manual — Section 2: Driving Safely
7. Hydroplaning can begin at speeds as low as what when a lot of water is on the road?
Correct answer: 30 mph
With enough standing water, the tires can lift off the surface and hydroplane at speeds as low as 30 mph, especially if pressure is low or tread is worn.
Source: Arizona CDL Manual — Section 2: Driving Safely
8. On packed snow, the manual says to reduce your speed by about how much?
Correct answer: One-half or more
Packed snow calls for cutting speed roughly in half, and truly icy pavement means slowing to a crawl and stopping as soon as it is safe.
Source: Arizona CDL Manual — Section 2: Driving Safely
9. Compared with a loaded truck, an empty truck generally needs what kind of stopping distance?
Correct answer: A greater stopping distance because of less traction
Heavy-vehicle brakes and tires work best under load; an empty truck has less traction, so it actually takes longer to stop than a loaded one.
Source: Arizona CDL Manual — Section 2: Driving Safely
10. Total stopping distance is the sum of which three parts?
Correct answer: Perception, reaction, and braking distance
Adding the distance traveled while your brain perceives the hazard, while you move your foot to react, and while the vehicle brakes gives the total stopping distance.
Source: Arizona CDL Manual — Section 2: Driving Safely
11. What is the correct response if your vehicle begins to hydroplane?
Correct answer: Ease off the accelerator and push in the clutch, without braking
To recover, let off the gas and depress the clutch so the wheels spin freely and slow down; braking during a hydroplane only makes things worse.
Source: Arizona CDL Manual — Section 2: Driving Safely
12. Going twice as fast, from 20 up to 40 mph, changes the braking distance how?
Correct answer: It becomes about four times longer
Doubling speed quadruples both the impact force and the braking distance; tripling the speed makes them nine times greater.
Source: Arizona CDL Manual — Section 2: Driving Safely
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Every Arizona question is written from the official Arizona 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