Key points
Alcohol reaches your brain in about 20 minutes and affects your judgment and skill.
Source: Handbook p. 122
“It reaches your brain in about 20 minutes. In your brain, alcohol affects those parts that control your judgment and skill.”
Louisiana Class D and E Driver's Guide, Handbook p. 122Black coffee, exercise or a cold shower will not sober you up.
Source: Handbook p. 122
“Black coffee, exercise or a cold shower will not sober you up.”
Louisiana Class D and E Driver's Guide, Handbook p. 122It takes about an hour for your body to get rid of one normal drink.
Source: Handbook p. 123
“It takes about an hour for the body to get rid of one normal drink from the circulatory system.”
Louisiana Class D and E Driver's Guide, Handbook p. 123The legal limit is .08 if you are 21 or older.
Source: Handbook p. 123
“.08 if you are 21 years of age or older”
Louisiana Class D and E Driver's Guide, Handbook p. 123The limit is .02 if you are 20 or younger, and .04 in a commercial vehicle.
Source: Handbook p. 123
“.04 if you are operating a commercial motor vehicle .08 if you are 21 years of age or older .02 if you are 20 years of age and younger”
Louisiana Class D and E Driver's Guide, Handbook p. 123The body processes 0.015% of alcohol per hour.
Source: Handbook p. 123
“The body can process 0.015% of alcohol per hour.”
Louisiana Class D and E Driver's Guide, Handbook p. 123Louisiana bans open alcohol containers and drinking in a vehicle.
Source: Handbook p. 124
“This law prohibits both the possession of any open alcoholic beverage container and consumption of any alcohol beverage in a vehicle.”
Louisiana Class D and E Driver's Guide, Handbook p. 124A first DWI conviction could cost you $4,500.
Source: Handbook p. 124
“Your first conviction could cost you $4,500”
Louisiana Class D and E Driver's Guide, Handbook p. 124
Numbers to know
| Number | What it means | Manual |
|---|---|---|
| 20 minutes | time for alcohol to reach the brain | Handbook p. 122 |
| 1 hour per drink | time for the body to get rid of one normal drink | Handbook p. 123 |
| .08 at 21; .02 at 20 and younger; .04 commercial | Louisiana BAC limits | Handbook p. 123 |
| 0.015% per hour | rate the body processes alcohol | Handbook p. 123 |
| $4,500 | possible total cost of a first DWI conviction | Handbook p. 124 |
3 questions from the Louisiana practice test
1. What BAC is the Louisiana legal limit for a driver age 21 or older?
- 0.15%
- 0.02%
- 0.04%
- 0.08%
Show answer
0.08%. For a driver who is 21 or older, Louisiana lists 0.08% as the legal BAC limit. The 0.02% figure applies to drivers 20 and younger, while 0.04% applies when operating a commercial motor vehicle. The 0.15% choice is not the ordinary adult threshold; it is a higher BAC level tied to a more severe administrative suspension after testing. The practical cue is to identify the driver's age and vehicle category before choosing a number. Alcohol can impair driving before the listed limit, so the safest plan is not to drive after drinking.
2. Which BAC does the Louisiana guide identify as the legal limit for drivers age 20 and younger?
- 0.04%
- 0.02%
- 0.08%
- 0.10%
Show answer
0.02%. Louisiana lists 0.02% as the legal BAC limit for a driver who is 20 or younger. The 0.08% figure belongs to drivers 21 or older, and 0.04% is the listed limit for a commercial motor vehicle. The 0.10% choice is not one of the guide's three age or vehicle thresholds. This is an age based rule, so do not substitute the adult limit when the driver is under 21. A young driver should treat any alcohol before driving as unsafe, even though the legal table supplies a specific numerical threshold.
3. According to the Louisiana guide, about how long does the body take to remove one normal drink from circulation?
- About three hours
- About fifteen minutes
- About one hour
- Only after a full night's sleep
Show answer
About one hour. The guide says the body takes about an hour to get rid of one normal drink from the circulatory system. That is an approximate processing statement, not a promise that a person will be safe or unimpaired after waiting exactly one hour. The shorter fifteen-minute choice understates the time, while three hours and a full night's sleep are not the guide's stated interval for one drink. Alcohol affects judgment and skill, and individual effects vary. The reliable driving cue is to arrange a sober ride instead of trying to calculate a safe departure time from drink count alone.
Practice this topic
Lock it in with alcohol and dui questions from the free Louisiana practice test. Every answer comes with a plain English explanation.
Source: the Louisiana Class D and E Driver's Guide, Chapter 9: Driving Offenses. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.