← CDL General Knowledge: Safe Driving Rules

CDL Commercial Drivers License General Knowledge Practice Test

Free 5-question sample test with instant feedback. See how ready you are.

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Sample Questions

Question 1

What is the minimum following distance in seconds a CDL driver should maintain when traveling at speeds under 40 mph?

Answer: At least one second for every 10 feet of vehicle length. For a 40-foot vehicle, that is 4 seconds minimum.

Question 2

How much additional following distance should a CDL driver add when traveling above 40 mph?

Answer: Add one additional second to the base following distance. For example, a 40-foot truck needs 5 seconds instead of 4 seconds above 40 mph.

Question 3

What is meant by 'hydroplaning' and at what speed can it begin to occur?

Answer: Hydroplaning occurs when tires ride on a film of water instead of the road surface, reducing traction to near zero. It can begin at speeds as low as 30 mph on wet roads.

Question 4

What is 'speed matching' and why is it important for CDL drivers on highways?

Answer: Speed matching means driving at the same speed as surrounding traffic when safe to do so. Vehicles moving slower or faster than traffic flow create greater crash risk.

Question 5

When driving on a slippery road, how should a CDL driver adjust their following distance?

Answer: Following distance should be increased to at least double the normal distance on slippery surfaces to allow for extended stopping distances.