In a dual air-brake system, you should let the air pressure build to at least what level before driving?
Correct. Wait until the system pressure is at least 100 psi before driving in a dual air-brake system.
CDL Practice Question #118
Category: Air Brakes
Why this question matters
This question is one of 71 in our Air Brakes bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.