6.1 How Alcohol & Drugs Affect Driving, BAC & Under-21 Laws

Each year in the United States, alcohol causes about 30 percent of all highway deaths. Massachusetts responds with some of the strictest operating-under-the-influence (OUI) laws in the country, and the permit exam tests both the science of impairment and the penalties.

Alcohol Is a Depressant

Whether it is beer, wine or liquor, alcohol is a depressant. It:

• Slows your reflexes and lengthens reaction time
• Distorts your vision and judgment
• Reduces coordination
• Makes you feel more confident, so you take chances you normally would not
• Makes you less likely to buckle up, more likely to speed and less able to stay in your lane

Even one drink in an hour can affect your driving, and fatigue, emotional upset or an empty stomach make it worse. No one is immune: trying to concentrate harder does not cancel the drug's effect. Plan a safe ride before drinking: a designated driver, a taxi, a rideshare app, or a call to family or friends.

Blood Alcohol Content (BAC)

Your liver and kidneys process alcohol, and that takes time. You do not digest it like food. Black coffee, a cold shower, exercise or eating may make you feel more alert, but none of them changes how fast alcohol leaves your body. Only time does.

BAC is the amount of unprocessed alcohol in your body, measured by a blood or breath test. It depends on:

• Your body weight
• How much you drank
• How much food you ate before drinking
• How long you have been drinking
• How fast your body processes alcohol, which differs from person to person

Standard Drinks

The type of drink does not matter; the amount of alcohol does. Each of these contains about half an ounce of alcohol:

Any one of them can raise an average person's BAC by about 0.02. Drinking more than one per hour makes BAC climb. For drivers under 21, that single drink can reach the 0.02 zero-tolerance level (Section 6.2).

Marijuana

Marijuana makes it harder to respond to sights and sounds and to handle a quick series of tasks. The most serious danger is reacting to something unexpected, such as a car pulling out of a side street or a child running between parked cars. It also causes a significant loss of night vision. Massachusetts has decriminalized some marijuana possession and use, but operating under the influence of marijuana is still a crime, and the full OUI penalty chart applies.

Other Drugs and Medicines

OUI laws apply to drugs as well as alcohol, including illegal drugs, prescriptions and over-the-counter medicines.

You can be charged with OUI on prescription drugs. It is illegal to drive impaired by any substance. Read labels, ask your doctor or pharmacist about side effects, and never mix alcohol with other drugs, because the combination dramatically increases impairment.

Under-21 Alcohol Laws

Drivers under 21 are twice as likely as other drivers to be in alcohol-related crashes, so Massachusetts law is stricter for them. If you are under 21, it is illegal to:

• Buy alcohol or have someone buy it for you
• Possess, carry or transport alcohol unless accompanied by a parent or guardian

The Open Container Law

You may not drink alcohol while driving, and you may not have an open alcoholic drink inside the vehicle, even if someone else is holding it.

• Conviction brings a $100 to $500 fine.
• A driver under 21 is arrested, fined and suspended.
• For a Junior Operator, drinking from an open container also triggers the extra Section 24P suspension (Section 2.3).

False or Altered Licenses and IDs

It is illegal to use a false license or ID, alter one, use someone else's, or give false information to obtain one. In most cases these are felonies, and penalties apply even if you never try to buy alcohol.

• Under M.G.L. chapter 90, section 22(e), the RMV can suspend your license up to six months without a conviction.
• A conviction brings a one-year suspension.
• Buying fake IDs online often leads to identity theft.