Prohibited equipment — Texas Permit Test
Prohibited equipment on the Texas permit test — 6 rules, each with the reason behind it and a question on it while it is fresh.
The rules
A red light showing from the front is not allowed except on an emergency vehicle.
Red at the front is how drivers pick an emergency vehicle out of traffic. Anything else wearing it steals that signal.
The following equipment is considered unsafe and is not allowed on your vehicle: 1. A red light showing from the front except on an emergency vehicle
A bell, siren, or exhaust whistle is not allowed except on an emergency vehicle.
A siren means get out of the way. A car that can make one without the right to use it is a hazard.
The following equipment is considered unsafe and is not allowed on your vehicle: 1. A red light showing from the front except on an emergency vehicle. 2. A bell, siren, or exhaust whistle except on an emergency vehicle
Nothing may extend more than three inches beyond the left side or six inches beyond the right side of the body, running board, or fenders.
Anything sticking out reaches into the next lane or over the curb. The allowance is wider on the right because that side faces away from traffic.
extending more than three inches beyond the left side or six inches beyond the right side of the body, running board, or fenders of your car
A radar interference device built to scramble or disrupt a speed-measuring radar or laser is not allowed.
This is equipment whose only purpose is defeating enforcement. Texas bans the device rather than the use.
A radar interference device designed, manufactured, used, or intended to be used to interfere with, scramble, disrupt, or cause to malfunction a radar or laser device used to measure a vehicle’s speed
A vehicle must not be modified or weighted so that the body sits below the lowest part of the wheel rims.
A body that low grounds out and catches on anything in the road. The rim is the floor Texas sets.
A vehicle must not be modified or weighted in such a manner where the body is below the lowest part of the rims of the wheels
Flashing red lights on the front are barred except on emergency vehicles, school buses, and church buses.
Buses that carry children get the same signal as an ambulance, because they stop in traffic for the same reason.
Flashing red lights on the front except on emergency vehicles, school buses, and church buses
On the test
Which vehicle may show a red light from the front in Texas?
An emergency vehicle. Red at the front is how drivers pick an emergency vehicle out of traffic. Anything else wearing it steals that signal. Texas Driver Handbook, p.16: “The following equipment is considered unsafe and is not allowed on your vehicle: 1. A red light showing from the front except on an emergency vehicle”
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
- One payment, once — not a subscription. Nothing renews and there is nothing to cancel, for an exam you sit one time.
- Free to start: a 10-question test and the first section of cards. No sign-up and no account.
- Paying opens the rest of the cards, unlimited full-length practice tests, and retests built from exactly the questions you got wrong.
- Every level up to Prepared — 3 tests passed in a row.
- Do the work, fail the real exam, and we refund you.
Where these come from
Every rule here is checked against Texas Driver Handbook, published by the Texas Department of Public Safety, and against the state code itself. Last checked 2026-09-16.
- src/assets/drivers-manuals/TX.pdf (Texas Driver Handbook, form DL-7, Revised January 2026, Texas Department of Public Safety, retrieved 2026-09-14 from dps.texas.gov)
- src/assets/drivers-manuals/TX.pages.txt (plain pdftotext over that PDF; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/SOURCES.json (sha256, folio offset 6, nonLawPages, the four extraction traps and the extraction flag, each with its measured basis)
- docs/plans/texas-exam-shape.md (the search that established that no official source states the question count, and the two decoys it disposes of)