The four-way flashers on a commercial vehicle should be used:
Correct. Use four-way flashers anytime your vehicle is stopped on or near the roadway, or moving slowly enough that approaching traffic might be surprised.
CDL Practice Question #37
Category: General Knowledge
Why this question matters
This question is one of 97 in our General Knowledge 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.