Many adults — by some estimates, nearly half the adult
population — choose never to drink alcohol, so they
never drive after drinking. For persons under 21,
it is against the law in every U.S. state to drink alcohol.
There are good medical, psychological and
developmental reasons for these laws.
The obvious way to eliminate the leading highway
safety problem is for people never to drink alcohol and
then drive. But what if people do? How much is “too
much” if someone plans to drive? It is a lot less
than many might think. Although it depends on each
person and situation, here is some general information
on the problem.
The Blood Alcohol Concentration (BAC) of someone
who is drinking depends upon four things:
The amount of alcohol consumed
The drinker’s body weight
The amount of food that is consumed before and
during drinking
The length of time it has taken the drinker to
consume the alcohol
According to the American Medical Association, a 180 lb
(82 kg) person who drinks three 12 ounce (355 ml)
bottles of beer in an hour will end up with a BAC
of about 0.06 percent. The person would reach thesame BAC by drinking three 4 ounce (120 ml) glasses
of wine or three mixed drinks if each had 1-1/2 ounces
(45 ml) of liquors like whiskey, gin, or vodka.
It is the amount of alcohol that counts. For example, if
the same person drank three double martinis (3 ounces
or 90 ml of liquor each) within an hour, the person’s
BAC would be close to 0.12 percent. A person
who consumes food just before or during drinking will
have a somewhat lower BAC level.
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There is a gender difference, too. Women generally
have a lower relative percentage of body water
than men. Since alcohol is carried in body water, this
means that a woman generally will reach a higher BAC
level than a man of her same body weight will when
each has the same number of drinks.
The law in most U.S. states, and throughout Canada,
sets the legal limit at 0.08 percent. In some other
countries, the limit is even lower. For example, it is
0.05 percent in both France and Germany. The
BAC limit for all commercial drivers in the United States
is 0.04 percent.
The BAC will be over 0.10 percent after three to
six drinks (in one hour). Of course, as we have seen, it
depends on how much alcohol is in the drinks, and
how quickly the person drinks them.
But the ability to drive is affected well below a BAC of
0.10 percent. Research shows that the driving skills
of many people are impaired at a BAC approaching
0.05 percent, and that the effects are worse at night. All
drivers are impaired at BAC levels above 0.05 percent.Statistics show that the chance of being in a collision
increases sharply for drivers who have a BAC of
0.05 percent or above. A driver with a BAC level of
0.06 percent has doubled his or her chance of having a
collision. At a BAC level of 0.10 percent, the chance
of this driver having a collision is 12 times greater; at a
level of 0.15 percent, the chance is 25 times greater!
The body takes about an hour to rid itself of the alcohol
in one drink. No amount of coffee or number of cold
showers will speed that up. “I will be careful” is not the
right answer. What if there is an emergency, a need
to take sudden action, as when a child darts into
the street? A person with even a moderate BAC might
not be able to react quickly enough to avoid the
collision.
There is something else about drinking and driving that
many people do not know. Medical research shows
that alcohol in a person’s system can make crash
injuries worse, especially injuries to the brain, spinal
cord, or heart. This means that when anyone who has
been drinking — driver or passenger — is in a crash,
that person’s chance of being killed or permanently
disabled is higher than if the person had not been
drinking.
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