Drinking and driving - never exceed the BAC (Blood Alcohol Concentration) limits for drivers
As with any other alcoholic beverage, the consumption of wine affects the capacity to perform certain activities, such as driving.
Blood Alcohol Concentration (BAC)
- BAC is the amount of alcohol in the blood stream:
- a BAC level of 0.5 means that an individual has 0.5g of alcohol in their body for every 1 litre of blood.
- Taking a standard drink of 10g of alcohol, BAC will generally increase by 0.2-0.3 for each standard drink.
- A BAC will generally decrease by approximately 0.2-0.1 per hour (¾ to 1 standard drink, or 8g of alcohol per hour).
- The BAC will increase sharply when alcohol is consumed on an empty stomach.
Absorption of alcohol
After an alcoholic drink is consumed, the alcohol is absorbed rapidly from the stomach and intestine into the bloodstream. The blood alcohol level after drinking a specific number of drinks depends on the rate of drinking and the rate at which it is broken down in the liver. The capacity of the liver to break down alcohol is limited, so that if there is more alcohol in the liver than it has capacity to break down, the remaining alcohol will circulate in the blood to other organs and tissues of the body, such as the brain. Alcohol usually starts to affect the brain within about 5 minutes of being swallowed.
The influence of alcohol on individuals will vary depending on the size, physical composition, gender, general health, metabolism, and/or the conditions under which alcohol is consumed (i.e. with or without food). For example, a woman’s BAC generally increases higher than a man’s because women tend to be smaller and have more fatty tissue per kg body weight than men. Men also have more body water, thus, alcohol is more concentrated in the blood of a woman consuming the same number of drinks as a man. In addition, women have leof the enzyme that metabolizes alcohol in their stomach and liver.
Because of the multitude of factors that affect BAC, it is very difficult to assess one’s own BAC or impairment. Alcohol steadily decreases a person’s ability to drive a motor vehicle safely. Listed below are some of the common negative consequences following the consumption of alcoholic beverages.
Impact of alcohol on the ability to drive
Consequences on the psychomotor functions of the driver
- Coordination and capacity to react decrease
- Capacity to judge speed, distance and the relative position of the vehicle is affected
- Capacity to follow a trajectory or to face an unexpected event is affected
Consequences on the vision of the driver
- Field of vision is reduced and peripheral vision is altered
- Recovery of sight after a flash is delayed
- Even with low alcohol levels in the blood, the capacity to see, follow, and accommodate objects is deteriorated
Consequences for behaviour and attitude
- Alcohol may alter driving behaviour and reactions may become aggressive or neglectful
- It may induce feelings of over-confidence, which can give rise to reckless decisions
For these reasons, all EU member states have established legal limits on the BAC for drivers (Figure 6).
The best advice is to avoid drinking alcoholic beverages if you drive. In any case, the BAC limits established for drivers should never be exceeded!