Facts About Blood
Alcohol Concentration (BAC)

What is BAC?

BAC is Blood Alcohol Concentration, or the amount of alcohol present in one’s blood system. BAC begins when an individual consumes even a minimal amount of alcohol, and increases exponentially with each drink consumed. BAC does not distinguish between "hard" liquor, wine or beer; any alcohol consumed will increase the BAC level within an individual.

How much is too much?

While individuals rarely possess the tools to determine their own BAC, law enforcement officials do, and will not hesitate to use them if they believe a driver to be impaired. BAC can vary with-in an individual, due to a number of physical and environmental factors, including, but not limit-ed to, height, weight, previous experience with alcohol and amount of food consumed prior to drinking. Because of the wide variance that exists between individuals, it is wise to make alternate travel plans or designate a driver, when even a minimal amount of alcohol is involved in any given situation.

At what BAC level does impairment begin?

Studies show that impairment begins at any BAC level over .00, and can affect an individual’s judgment and ability to react, factors that are critical to safe driving. While it is true that accepted BAC levels vary from state to state, to ensure the well-being of all those on the road, the only truly safe driving is sober driving.

Real change will not take place until the public recognizes that driving under the influence, at any BAC level, endangers the life of the driver, his/her passengers, and all those traveling on the road. The physical, emotional and economic burdens impaired drivers inflict upon the community each year are unparalleled.

Common Symptoms People Exhibit at Various BAC Levels,
and the Probable Effects On Driving Ability


Blood Alcohol

Typical Effects Predictable Effects
on Driving


  • Some loss of judgment
  • Relaxation
  • Slight body warmth
  • Altered mood
  • Decline in visual functions (rapid tracking of a moving target)

  • Decline in ability to perform two tasks at the same time (divided attention)

  • Exaggerated behavior

  • May have loss of small-muscle control (e.g. focusing your eyes)

  • Impaired judgment

  • Usually good feeling

  • Lowered alertness

  • Release of inhibition

  • Reduced coordination

  • Reduced ability to track moving objects

  • Difficulty steering

  • Reduced response to emergency driving situations

  • Muscle coordination becomes poor (e.g. balance, speech, vision, reaction time, and hearing)

  • Harder to detect danger

  • Judgment, self-control, reasoning, and memory are impaired.

  • Concentration
  • Short-term memory loss
  • Speed control
  • Reduced information processing capability (e.g. signal detection, visual search)
  • Impaired perception


  • Clear deterioration of reaction time and control
  • Slurred speech, poor coordination, and slowed thinking
  • Reduced ability to maintain lane position and brake appropriately
  • Far less muscle control than normal
  • Vomiting may occur (unless this level is reached slowly or a person has developed tolerance for alcohol)
  • Major loss of balance
  • Substantial impairment in vehicle control, attention to driving task, and in necessary visual and auditory information processing

1 The table is from The ABCs of BAC brochure from The National Highway Traffic Administration located at www.nhtsa.dot.gov.

Above information provided by the The National Highway Traffic Safety Administration.

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