Drinking & Driving
Drinking and 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 0.5 g of alcohol in his/her 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 women and 0.1-0.2 for men for each standard drink
· A BAC will generally decrease by approximately 0.2-0.1 per hour (¾ to 1 standard drink, or 8 g of alcohol per hour)
· The BAC will increase sharply when alcohol is consumed on an empty stomach
Absorption and metabolism 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 by the enzyme alcohol dehydrogenase or ADH. The capacity of the liver to break down alcohol is limited, so if the liver has to handle more alcohol than its capacity for 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.
Even small amounts of alcohol can influence the ability to drive, so the only safe advice is to avoid any alcohol if driving. The influence of alcohol on individuals varies depending on:
1. body weight
2. gender (men process alcohol faster than women)
3. how fast you drink
5. age and/or
6. 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 since women tend to be smaller and have more fat tissue per kg body and less body water compared to men. Consequently, alcohol is more concentrated in the woman’s blood consuming the same amount of alcohol as a man. In addition, women have less of 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 the 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.
How alcohol affects driving
Many of the functions that are needed to drive safely are affected when alcoholic beverages are consumed: the brain takes longer to receive messages from the eye; processing information becomes more difficult; and instructions to the body's muscles are delayed resulting in slower reaction times.
Blurred and double vision can also occur, which means the ability to see things correctly while driving is reduced. Individuals are also more likely to take potentially dangerous risks behind the wheel if they've been drinking alcoholic beverages.
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
Driving while either intoxicated or drunk is dangerous and drivers with high blood alcohol concentration (BAC) are at greatly increased risk of car accidents, highway injuries and vehicular deaths. It is recommended not to drive when drinking. In most European countries, the limit is usually 0.5 g per 1 l of blood. For novice drivers, in some countries, limit is 0 g.
An updated and comprehensive international BAC limits table can be found on the International Center for Alcohol Policies (ICAP) website. For more information and data on European Road Safety you can also visit the European Commission DG Mobility and Transport website.
The above summary provide an overview of the topic, for more details and specific questions, please refer to the articles in the database.