When inspecting a doubles rig, the lights on the rear of the rear-most trailer must:
Correct. Brake, turn, and marker lights at the rear of the rearmost trailer must be working and visible — that is what following traffic sees.
CDL Practice Question #376
Category: Doubles/Triples
Why this question matters
This question is one of 50 in our Doubles/Triples 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.