Alcohol, drugs and the law

Key points

1. Alcohol is involved in approximately 40% of fatal crashes.

   Source: Handbook p. 71

   “Alcohol is involved in approximately 40% of fatal crashes.”
   Montana Driver Manual, Handbook p. 71

2. The average body processes one drink per hour, and alcohol can still build up at that rate.

   Source: Handbook p. 71

   “The average person’s body will process one alcoholic drink in one hour. Alcohol can still accumulate in your body even if you are drinking at a rate of one drink per hour.”
   Montana Driver Manual, Handbook p. 71

3. One drink is 1 1/2 ounces of 80 proof liquor, 12 ounces of beer, or a 5 ounce glass of wine.

   Source: Handbook p. 71

   “One alcoholic drink is: 1-1/2 ounces of 80-proof liquor (one shot glass), straight or with a mixer; 12 ounces of commercial beer (a regular size can, bottle, mug or glass); or a 5-ounce glass of wine.”
   Montana Driver Manual, Handbook p. 71

4. You must be 21 to buy or drink alcohol.

   Source: Handbook p. 72

   “You are not allowed to buy or consume alcohol unless you are 21 years of age or older.”
   Montana Driver Manual, Handbook p. 72

5. You can be arrested with a BAC of 0.08% or more. For drivers under 21 the limit is 0.02.

   Source: Handbook p. 72

   “You can be arrested for driving with a blood alcohol concentration (BAC) of 0.08% or more, or while driving under the influence. BAC is the percentage of alcohol in your blood, and is usually determined by a breath, blood, or urine test. The BAC for a driver under 21 years of age is 0.02.”
   Montana Driver Manual, Handbook p. 72

6. If an officer asks you to take a BAC test you must; refusing can cost you your license.

   Source: Handbook p. 72

   “If a police officer asks you to take a test, you must do so. You can lose your driver license if you refuse to take a BAC test.”
   Montana Driver Manual, Handbook p. 72

7. A first conviction brings a $300 to $1000 fine, 1 to 60 days in jail, and a six month suspension.

   Source: Handbook p. 72

   “you will be fined from $300 to $1000, plus court charges; you could be sentenced to 1 to 60 days in jail; and your license will be suspended for six months.”
   Montana Driver Manual, Handbook p. 72

8. Open containers must be kept in a locked glove compartment, the trunk, or behind the last upright seat.

   Source: Handbook p. 72

   “In a locked glove compartment or storage compartment; ■ In a trunk, luggage compartment, truck bed or cargo compartment; or ■ Behind the last upright seat”
   Montana Driver Manual, Handbook p. 72

9. A drug label warning about operating heavy machinery means do not drive.

   Source: Handbook p. 73

   “Drug warnings about operating heavy machinery mean DO NOT DRIVE YOUR CAR OR TRUCK.”
   Montana Driver Manual, Handbook p. 73

10. Report a suspected drunk driver toll free at 1-800-525-5555.

    Source: Handbook p. 72

    “If you see someone you suspect of driving while intoxicated, or need to report an accident, you may call toll free 1-800-525-5555.”
    Montana Driver Manual, Handbook p. 72

Numbers to know

3 questions from the Montana practice test

1. 1. At what BAC can a driver be arrested for driving with an unlawful alcohol concentration in Montana?

   1. 0.16% or more only
   2. 0.02% or more for every driver
   3. 0.08% or more
   4. 0.05% or more
   Show answer

   0.08% or more. Montana treats a BAC of 0.08% or more as enough for an arrest for driving with that alcohol concentration. The 0.02% figure belongs to drivers under 21, so it is not the general adult threshold. A reading of 0.16% is not needed before enforcement can begin, and 0.05% is below the stated adult threshold. On a test question, separate the ordinary adult number from the special under-21 rule before choosing.

2. 2. What does the Montana manual count as one alcoholic drink?

   1. A 16 ounce beer
   2. Two shots
   3. 1.5 ounces of 80 proof liquor, 12 ounces of beer, or a 5 ounce glass of wine
   4. Any amount under 8 ounces
   Show answer

   1.5 ounces of 80 proof liquor, 12 ounces of beer, or a 5 ounce glass of wine. One alcoholic drink is 1.5 ounces of 80 proof liquor, a shot glass, straight or mixed; 12 ounces of commercial beer; or a 5 ounce glass of wine, each with about the same alcohol. The BAC limit for a driver under 21 is 0.02, and only time lowers BAC. In Montana, half of all traffic fatalities are alcohol related, so arrange a sober ride before drinking.

3. 3. Where may an open alcoholic beverage container be kept in a Montana vehicle?

   1. In the driver's door pocket if it has a lid
   2. In an unlocked cup holder beside the driver
   3. On the floor behind the front passenger seat
   4. In a locked glove compartment or storage compartment
   Show answer

   In a locked glove compartment or storage compartment. An open alcoholic beverage container must be kept in a locked glove compartment or storage compartment, among the lawful storage locations listed by Montana. An unlocked cup holder, a door pocket, and a floor area in the passenger compartment leave the container accessible. The key detail is that the compartment must be locked, not merely covered or located away from the driver’s hand. Check the storage location before driving on a highway.

Source: the Montana Driver Manual, Chapter 6: Physical Requirements. 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.