General Knowledge · Section 2.6

Speed and stopping distance: CDL practice questions

Section 2.6 covers how far a heavy vehicle travels before it stops, and how road surface, curves, sight distance and traffic should set your speed. These questions are part of the General Knowledge test.

Examlane has 28 questions on this chapter. Ten are below; open one to see the answer and why. The rest are in the practice tests.

Practice this chapter

1. Why does an empty truck need a longer stopping distance than a fully loaded truck?
1. An empty vehicle has less traction
2. An empty vehicle's brakes must absorb more heat
3. An empty vehicle's springs and shock absorbers lock up without a load
4. An empty vehicle's driver needs more time to see hazards
Answer: A. An empty vehicle has less traction
An empty truck has less traction, so it needs a longer distance to stop.
Based on: CDL manual, Section 2.6.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
2. On a wet road, by about how much should you reduce your speed?
1. About one-tenth
2. About one-half
3. About one-third
4. About two-thirds
Answer: C. About one-third
On a wet road, cut your speed by about one-third, for example from 55 to about 35 mph.
Based on: CDL manual, Section 2.6.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
3. It is colder than freezing outside and the road surface looks wet. What should you watch for?
1. Loose gravel under the water
2. Black ice
3. Oil that mixes with fresh rain
4. Heavy fog near the pavement
Answer: B. Black ice
Below freezing, a road that looks wet may be covered by black ice, a thin clear layer you can see through.
Based on: CDL manual, Section 2.6.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
4. Your vehicle is hydroplaning. What is the best way to regain control?
1. Brake hard to slow down quickly
2. Turn the steering wheel sharply back and forth
3. Press the accelerator to push through the water
4. Release the accelerator and push in the clutch
Answer: D. Release the accelerator and push in the clutch
To regain control in a hydroplane, ease off the accelerator and push in the clutch so the wheels turn freely. Braking makes it worse.
Based on: CDL manual, Section 2.6.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
5. Why is braking in the middle of a curve dangerous?
1. It makes the wheels lock up more easily and start a skid
2. Other drivers cannot see your brake lights in a curve
3. It makes the engine lose power
4. It pulls the vehicle toward the inside of the curve
Answer: A. It makes the wheels lock up more easily and start a skid
Braking in a curve can lock the wheels more easily and cause a skid, so slow down before you enter.
Based on: CDL manual, Section 2.6.3 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
6. You must switch to low beams at night. What should you do about your speed?
1. Keep the same speed, because the road has not changed
2. Speed up so you pass through the dark area quickly
3. Slow down
4. Follow closely behind another vehicle to use its lights
Answer: C. Slow down
Low beams light less of the road than high beams, so you must drive slowly enough to stop within what you can see.
Based on: CDL manual, Section 2.6.4 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
7. In heavy traffic, which speed is generally safest?
1. Faster than other vehicles, so you pass them quickly
2. The speed of the other vehicles
3. The slowest speed you can hold
4. The posted limit, even when traffic is slower
Answer: B. The speed of the other vehicles
In heavy traffic the safest choice is to drive at the speed of traffic, as long as that speed is legal and safe.
Based on: CDL manual, Section 2.6.5 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
8. What is the principal way to control your speed on a downgrade?
1. Light, steady pressure on the foot brake the whole way
2. Coasting in neutral
3. The parking brake
4. The braking effect of the engine
Answer: D. The braking effect of the engine
Use the engine's braking effect as the main way to control speed on a downgrade, and save the service brakes for slowing or stopping.
Based on: CDL manual, Section 2.6.6 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
9. Which factor causes more injuries and deaths in road construction zones than any other?
1. Speeding traffic
2. Poor lighting
3. Loose gravel on the road
4. Faded road signs
Answer: A. Speeding traffic
Excess speed causes more injuries and deaths in work zones than anything else, so obey the posted limits.
Based on: CDL manual, Section 2.6.7 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.
10. At 55 mph, what is the total minimum distance your vehicle travels to come to a complete stop?
1. 142 feet
2. 216 feet
3. 358 feet
4. 419 feet
Answer: D. 419 feet
Perception, reaction and braking distance add up to a minimum of 419 feet at 55 mph.
Based on: CDL manual, Section 2.6.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

Read the chapter itself in your state's CDL manual, Section 2.6. Your state's manual is free: find it in the state table.

More General Knowledge chapters: Railroad crossings, Vehicle inspection, Managing space, Driving emergencies, Cargo weight and securement.