New Hampshire CDL — General Knowledge practice
New Hampshire 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
12 questions · pass with 10 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. What does the manual say about the time saved by driving faster than the flow of traffic?
Correct answer: Not much time is saved, and the added risk is not worth it
Saving time is the main reason drivers speed, but going faster than traffic saves little. It means constant passing, more crash risk and more fatigue.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.5, Speed and Traffic Flow
2. By the manual's figures, how far does a vehicle going 55 mph travel during the average perception time of an alert driver?
Correct answer: 142 feet
An alert driver's perception time averages 1 3/4 seconds, which is 142 feet at 55 mph. Reaction adds 61 feet and braking about 216, for 419 in all.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.1, Stopping Distance
3. Why can an empty truck need a longer distance to stop than a loaded one?
Correct answer: An empty vehicle has less traction
A heavy vehicle's brakes, tires, springs and shocks are built to work best under a full load. Empty, the vehicle has less traction.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.1, Stopping Distance
4. The manual compares hydroplaning to which activity?
Correct answer: Water skiing
Hydroplaning is likened to water skiing: the tires ride up on water or slush and have little or no grip on the road.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.2, Matching Speed to the Road Surface
5. What does the manual say happens to brake linings when they are hot?
Correct answer: They wear faster
Hot linings wear faster, and heavily used brakes can go out of adjustment quickly. That is why adjustment needs frequent checks.
Source: New Hampshire Commercial Driver's License Manual — Section 2.16.3, Brake Fading or Failure
6. The manual says drivers who were dialing a phone covered 306 feet, roughly a football field, with their eyes off the road. At what speed is that figure calculated?
Correct answer: 55 mph
Dialing drivers looked away for 3.8 seconds on average. At 55 mph that works out to 306 feet.
Source: New Hampshire Commercial Driver's License Manual — Section 2.9.4, Cell/Mobile Phones
7. A road is at its slickest just after rain begins. What does the manual say happens if the rain keeps falling?
Correct answer: It washes the oil away
The first rain mixes with oil that vehicles have left on the road. Continued rain washes that oil away.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.2, Matching Speed to the Road Surface
8. Using the manual's downgrade braking technique with a "safe" speed of 40 mph, when do you first put the brakes on?
Correct answer: When your speed has climbed to 40 mph
In the proper low gear you leave the brakes alone until you reach the safe speed, then brake down to about 35 mph, release, and repeat.
Source: New Hampshire Commercial Driver's License Manual — Section 2.16.4, Proper Braking Technique
9. Compared with 20 mph, what does tripling your speed to 60 mph do to impact and braking distance?
Correct answer: They become nine times greater
Doubling from 20 to 40 mph makes them four times greater. Tripling to 60 mph makes them nine times greater.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.1, Stopping Distance
10. Which part of total stopping distance does the manual put at 61 feet for a vehicle going 55 mph?
Correct answer: Reaction distance
Reaction distance, covered in the 3/4 second to 1 second it takes to get on the brakes, comes to 61 feet at 55 mph.
Source: New Hampshire Commercial Driver's License Manual — Section 2.6.1, Stopping Distance
11. A driver of a 50-foot rig says five seconds of following distance is enough at any speed. By the manual's rule, when is that too little?
Correct answer: At speeds above 40 mph, where one more second is needed
The rule is one second per 10 feet of vehicle length below 40 mph, plus one more second at greater speeds. A 50-foot rig needs six seconds above 40 mph.
Source: New Hampshire Commercial Driver's License Manual — Section 2.7.1, Space Ahead
12. Partway down a steep grade, a driver with a manual transmission tries to downshift after speed has already built up. What does the manual warn may happen?
Correct answer: The driver may be unable to get into any gear, losing all engine braking
The lower gear will not go in, and you might end up with no gear at all, which means no engine braking. Shift down before the grade.
Source: New Hampshire Commercial Driver's License Manual — Section 2.16.2, Select the Right Gear before Starting Down the Grade
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