Traffic Laws

Study questions with answers

2 sample Traffic Laws questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. With the engine off and the foot brake fully applied, what is the most air a single vehicle should lose in one minute?

   Correct answer: No more than 3 psi

   Holding the foot brake down, a single vehicle should not drop more than 3 psi in one minute (a combination vehicle, no more than 4 psi); more than that means leaks to fix before driving.

   Source: South Carolina CDL Manual — Section 5.3.3: Final Air Brake Check

2. 2. During the air leakage test on a single vehicle, with the engine off and the parking brake released, the pressure drop should be no more than how much per minute?

   Correct answer: Less than 2 psi in one minute

   With a fully charged system and the parking brake released, a single vehicle should lose under 2 psi per minute (a combination vehicle, under 3 psi per minute).

   Source: South Carolina CDL Manual — Section 5.3.3: Final Air Brake Check