Alcohol and Louisiana's BAC limits

Key points

1. 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. 122

2. Black 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. 122

3. It 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. 123

4. The 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. 123

5. The 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. 123

6. The 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. 123

7. Louisiana 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. 124

8. A 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

3 questions from the Louisiana practice test

1. 1. What BAC limit applies to a Louisiana driver who is 21 years of age or older?

   1. .08 percent
   2. .02 percent
   3. .04 percent for every driver
   4. .10 percent
   Show answer

   .08 percent. For a driver age 21 or older, Louisiana identifies .08 percent as the legal BAC limit. The .02 figure belongs to drivers age 20 and younger, while .04 applies to a commercial motor vehicle operator. A reading of .10 is above the adult limit and is not the number to memorize for this category. The practical cue is to match the BAC number to the driver's age before choosing a response, because the guide separates adult, underage, and commercial driving rules. Impairment can begin before the legal threshold; even one drink can affect driving, so do not drive after drinking.

2. 2. Which BAC limit does the Louisiana guide list for a driver who is 20 years old or younger?

   1. .15 percent
   2. .08 percent
   3. .04 percent
   4. .02 percent
   Show answer

   .02 percent. Louisiana lists .02 percent for drivers who are 20 years old or younger. That threshold is different from the .08 percent adult limit and the .04 percent commercial motor vehicle limit. Selecting .08 overlooks the age distinction, while .04 describes another operating category. The age wording is the useful memory cue: when the question says 20 or younger, look for .02 rather than applying the adult figure automatically.

3. 3. According to the Louisiana guide, about how long does the body take to remove one normal drink from circulation?

   1. About three hours
   2. About fifteen minutes
   3. About one hour
   4. 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.

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.