BAC limits and elimination — Louisiana Permit Test
BAC limits and elimination on the Louisiana permit test — 7 rules, each with the reason behind it and a question on it while it is fresh.
The rules
In Louisiana, the legal blood alcohol limit for a driver 21 years of age or older is .08.
At .08 a driver 21 or older is legally drunk, but driving skills start to slip well before that point.
.08 if you are 21 years of age or older
In Louisiana, the legal blood alcohol limit for a driver 20 years of age or younger is .02.
Young drivers are new to the road, so the limit for anyone 20 or younger is set much lower than for adults.
.02 if you are 20 years of age and younger
In Louisiana, the legal blood alcohol limit for someone driving a commercial motor vehicle is .04.
A big truck can do great harm in a crash, so its driver is held to half the usual adult limit.
.04 if you are operating a commercial motor vehicle
It takes about an hour for the body to get rid of one normal drink, so after four drinks you should wait four hours or more before driving.
Your liver works at a set pace. Nothing speeds it up, so the only fix is to wait.
Therefore, if someone has had four normal drinks, they should wait four hours or more before they drive.
The body can process only about 0.015% of alcohol per hour.
Alcohol leaves the blood slowly, so a person can still be impaired many hours after the last drink.
The body can process 0.015% of alcohol per hour.
A person whose BAC is 0.20% at 2:00 a.m. will still be at 0.05% at noon the next day.
Heavy drinking at night can leave you unfit to drive the next morning, even after sleep.
and still 0.05% at noon the following day!
BAC can be measured simply by analyzing exhaled breath, such as with a breathalyzer; a blood sample is not needed for most legal purposes.
Police can check your alcohol level at the roadside with a breath test, so there is no hiding it.
It can be measured much more simply by analyzing exhaled breath (such as using a breathalyzer).
On the test
What is Louisiana's legal blood alcohol limit for a driver 21 years of age or older?
0.08%. At .08 a driver 21 or older is legally drunk, but driving skills start to slip well before that point. Class D & E Driver's Guide, p.123: “.08 if you are 21 years of age 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 Class D & E Driver's Guide, published by the Louisiana Department of Public Safety, and against the state code itself. Last checked 2026-10-04.
- src/assets/drivers-manuals/LA.pdf (Class D & E Driver's Guide, DPSMV2052 (R08/25), Louisiana Office of Motor Vehicles, retrieved 2026-09-14; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/LA.pages.txt (the plain pdftotext fixture every citation here was cut from and verified against; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/LA-exam.html (the OMV's Permits page, https://expresslane.la.gov/omv/drivers/personal-driver-s-licenses/permits/, archived 2026-10-04; the 40-question count)
- https://expresslane.la.gov/omv/resources/driver-manuals/
- https://expresslane.la.gov/omv/drivers/personal-driver-s-licenses/new-licenses/ (read 2026-10-04; "An 80% is the minimum passing score for the knowledge test.")