Modern trucks have ABS that is required on:
Correct. Federal rule: tractors built after March 1, 1997, and trailers and single-unit air-braked vehicles after March 1, 1998, must have ABS.
CDL Practice Question #159
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.