- A Only at fueling stations
- B Only when an inspector is present
- C Only on dirt roads
- D When parking on grades or dropping a trailer Correct answer
Why this is the correct answer
Chocks prevent rolling during uncoupling and on grades. They are inexpensive insurance against runaway trailers.
How this topic appears on the test
The Combination Vehicles CDL exam covers Coupling as a recurring theme. Test-writers favor questions that probe whether the applicant has internalized the safe operating procedure, not merely memorized the rule. When you encounter a question on this topic, slow down and verify that the answer you've chosen describes what a careful, defensive driver would actually do — not what is technically permissible.
If you missed this question, that's exactly the right outcome of a practice session: the goal is to surface gaps before the actual test. Open your state CDL manual to the Coupling section and re-read the relevant subchapter. Then come back and run through the rest of the Combination Vehicles practice exam.
For drivers preparing for the Combination Vehicles CDL exam, additional context — including federal manual excerpts, employer hiring practices, and DOT medical guidance — is widely available from industry resources. Continue reading on a recommended industry resource for further detail. Always cross-check anything you read with the current edition of your state CDL manual, since enforcement guidance is updated periodically.