Field answer
Direct answer
Choose a gear low enough before the downgrade to control speed without riding the service brakes; exact gear depends on weight, grade, transmission, road, and company procedure. Use the current equipment manual, code book, employer procedure, and qualified supervision before applying this on live work.
How to use this answer
Read the answer once, then prove it by choosing an answer in a practice question before looking at the explanation. If the miss repeats, tag the domain as Mountain driving and drill a smaller set before returning to mixed practice.