Mud flaps and safety chains — Montana Permit Test
Mud flaps and safety chains on the Montana permit test — 3 rules, each with the reason behind it and a question on it while it is fresh.
The rules
Mud flaps or fenders on the rearmost wheels must reach down to no more than 20 inches above the road when the vehicle is empty.
Flaps that hang too high let tires fling rocks into the windshield behind.
Trucks, buses, truck trailers, trailers/semi-trailers, or pole trailers, or vehicles of 8000 pounds or less GVW shall have fenders, splash aprons, or flaps on the rear most wheels or set of wheels, that extend down to a point not more than 20 inches above the surface of the highway, when the vehicle is empty.
Every trailer of 3,000 pounds GVW or less must have a steel chain or cable on the front, fastened securely to the towing unit.
If a light trailer's hitch pops off with no chain, the trailer wanders loose across the road.
Every trailer, semi-trailer or pole trailer of 3000 pounds GVW or less must have on the front a steel chain or cable, which shall be fastened securely to the towing unit.
A trailer's safety chain or cable must be no less than 1/4 inch in diameter.
A thin chain snaps the moment the hitch fails and the trailer's weight hits it.
Such chain or cable shall be no less than 1/4 inch in diameter.
On the test
Mud flaps must reach down to no more than how high above the road when the vehicle is empty?
20 inches. Flaps that hang too high let tires fling rocks into the windshield behind. Montana Driver Manual, p.17: “Trucks, buses, truck trailers, trailers/semi-trailers, or pole trailers, or vehicles of 8000 pounds or less GVW shall have fenders, splash aprons, or flaps on the rear most wheels or set of wheels, that extend down to a point not more than 20 inches above the surface of the highway, when the vehicle is empty.”
How this works
Most practice tests hand you a bank of questions and leave the manual somewhere else. This one puts them together.
You read one law and the reason behind it, then answer a question on that law while it is still fresh. Get it right and you move on; get it wrong and you have found the gap while it is cheap to fix, not on the morning of the exam.
Learning one rule at a time, and proving it immediately, is what turns a manual you skimmed into something you actually know — and it makes studying feel like getting somewhere rather than like waiting to find out.
What it costs
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Where these come from
Every rule here is checked against Montana Driver Manual, published by the Montana Department of Justice, and against the state code itself. Last checked 2026-10-04.
- src/assets/drivers-manuals/MT.pdf (Montana Driver Manual, Revised April 2024, Montana Department of Justice, Motor Vehicle Division, retrieved 2026-09-14 and re-checked 2026-10-04; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/MT.pages.txt (scripts/mt-text.sh: pdftotext -layout except printed pp.24-26, which are plain; the fixture every citation here was cut from and verified against; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/MT-exam.html (Administrative Rules of Montana 23.3.121, Road Signs and Road Rules, as reproduced by the Legal Information Institute, read 2026-10-04; states the seven-miss pass mark; sha256 pinned under examSource)
- https://mvdmt.gov/forms-driver-license/ (read 2026-10-04; links the manual)