General Knowledge · Question #42

What is the proper way to test the service brakes on a tractor?

A. Roll forward at 5 mph and apply the brakes firmly
B. Slam them at high speed
C. Test only at the destination
D. Test by listening for noise

Correct answer: A. Roll forward at 5 mph and apply the brakes firmly
Explanation: Roll at about 5 mph and apply brakes firmly to check for proper stopping and pulling.

Why this question matters on the General Knowledge exam

This question is one of the 65 we have for the General Knowledge CDL knowledge test. The official AAMVA Commercial Driver License Manual chapter on General Knowledge covers exactly this topic, and most state DMV exams pull from the same chapter. Memorizing the right answer is fine for passing, but understanding the underlying rule is what keeps you safe on the road and out of trouble with FMCSA inspectors.

If this topic gave you trouble, take the full General Knowledge practice test to drill it across all the related questions. We recommend reading every explanation, even on the questions you got right, because the manual phrasing in the explanation often shows up word-for-word on the real exam.

Take the full General Knowledge practice test →