DUI law — Idaho Permit Test
DUI law on the Idaho permit test — 12 rules, each with the reason behind it and a question on it while it is fresh.
The rules
Under Idaho law you are driving under the influence if your blood-alcohol concentration is .08 or more and you are 21 or older.
It is the figure everything else is measured against, and it applies from the driver's twenty-first birthday.
.08 or more if you are 21 or older
Under Idaho law you are driving under the influence if your blood-alcohol concentration is .02 or more and you are under 21 years of age.
It is a quarter of the adult figure, which in practice means a driver under 21 cannot drink at all.
(BAC) is .02 or more if you are under 21 years of age
Under Idaho law you are driving under the influence if your blood-alcohol concentration is .04 or more and you are operating a commercial vehicle.
The commercial figure sits between the two, because the vehicle is heavier and the driver is at work.
.04 or more if you are operating a commercial vehicle
An alcohol concentration of .20 or more carries even stiffer penalties in Idaho.
It is a separate, higher threshold above the ordinary limit, with its own consequences.
An alcohol concentration of .20 or more carries even stiffer penalties
Even if your BAC is less than .08 you may be convicted of driving under the influence of other intoxicating substances.
The number is not a safe harbor; it is only one of the ways a driver can be over the line.
Even if your BAC is less than .08, you may be convicted of driving under the influence of other intoxicating substances
A first DUI conviction brings up to six months in jail, a fine of up to $1,000, and a mandatory license suspension of at least 90 days and up to 180 days, with absolutely no driving privileges for the first 30 days.
The first offense already carries a jail term, which most drivers do not expect.
up to a $1,000 fine
A first DUI conviction brings a mandatory license suspension of at least 90 days and up to 180 days, or one year if the driver is under 21.
A driver under 21 loses the license for far longer on the same offense.
(one year if you are under 21)
A second DUI conviction within 10 years brings a mandatory jail sentence from 10 days to one year, a fine of up to $2,000, and a mandatory license suspension of one year.
The jail term stops being a maximum and becomes a minimum on the second conviction.
up to a $2,000 fine
A second DUI conviction within 10 years brings a mandatory jail sentence of 30 days if the driver is under 21.
The minimum jail term triples for a driver under 21 on the same second offense.
Mandatory jail sentence from 10 days to one year (30 days if you are under 21)
Three or more DUI convictions within 10 years bring a mandatory jail sentence from 30 days to ten years, a fine of up to $5,000, and a license suspension from one to five years. This conviction is a felony.
At the third conviction it stops being a traffic matter and becomes a felony record.
This conviction is a felony
An ignition interlock restriction will likely be required after the suspension for a DUI conviction.
The device follows the suspension rather than replacing it, at every level of conviction.
An ignition interlock restriction will likely be required after the suspension
There are enhanced penalties for CDL drivers who drive under the influence, up to the lifetime loss of CDL privileges.
For a commercial driver the license is the job, and it can be gone for good.
There are enhanced penalties for CDL drivers who drive under the influence, up to the lifetime loss of CDL privileges
On the test
What is the DUI alcohol concentration for an Idaho driver aged 21 or older?
.08 or more. It is the figure everything else is measured against, and it applies from the driver's twenty-first birthday. July 2026 Idaho Driver's Handbook, p.131: “.08 or more if you are 21 or older”
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 July 2026 Idaho Driver's Handbook, published by the Idaho Transportation Department, and against the state code itself. Last checked 2026-09-16.
- src/assets/drivers-manuals/ID.pdf (July 2026 Idaho Driver's Handbook, Idaho Transportation Department, retrieved 2026-09-14)
- src/assets/drivers-manuals/ID.pages.txt (pdftotext -layout over that PDF; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/SOURCES.json (sha256, folio offset 0, folioMarker, nonLawPages and the extraction flag, each with its basis)