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The Science of Drink Driving

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Drink driving science

A large proportion of traffic accidents are caused because the driver is inhibited by alcohol, and for young Europeans, drink driving is one of the main causes of death. It is for this reason that it is standard procedure to test any driver that has been in an accident for alcohol inhibition. The risk of a traffic accident when driving under the influence of alcohol increases exponentially as blood alcohol concentration rises.


What is it about alcohol that causes increased risk while driving?

Alcohol is a psychoactive substance, which means that it can cross the blood-brain barrier and directly influence the cells in the central nervous system. By influencing the ability for the brain to transmit signals, alcohol has a notable effect on people’s behaviour.

A blood alcohol concentration of 0.06% (still legally able to drive under UK drink driving law) causes a significant impairment in concentration, depth perception, peripheral vison, and risk taking. It is a combination of these factors that makes drink driving so dangerous.


Alcohol and the brain

Alcohol is a depressant, which means that it reduces the speed of transmission between neurons. It is well known that reaction speed quickly deteriorates as people get drunk. This is because signals take longer to transmit from the areas of the brain responsible for sensing to the areas of the brain responsible for responding. There are specific regions of the brain that are known to be affected by alcohol, which allows us to understand the effects in more detail. These are the cerebellum, the reticular activating system, the hippocampus and the pre-frontal cortex.

The cerebellum is at the back of the brain, and is responsible for motor control and balance. When this is inhibited by the effects of alcohol, people start to fall over. Before the invention of breathalysers, police used to ask drivers to walk in a straight line to see if they had any impairment. The ability to have accurate motor control is essential to driving, as there are many complex movements that are happening at the same time. Accurate use of the steering wheel, peddles, and gear stick are all required for safe driving. Alcohol directly hinders these skills.

The reticular activating system is involved in keeping people awake. People with damage to this area of the brain can develop disorders such as clinical insomnia or narcolepsy. When people have very high levels of blood alcohol the inhibition of this area of the brain can cause people to pass out, and even after a few drinks people can start to feel tired and drowsy. A large proportion of deaths from driving are caused by people falling asleep at the wheel, with alcohol as a likely cause.

The hippocampus is linked with short term memory formation. A famous case of a man who had his hippocampus removed inspired the film Memento. This patient was unable to form new memories. Alcohol can cause this same problem with people, and forgetting what happened the night before is a common symptom of heavy drinking. Rather than forgetting what happened, while under the influence the brain is unable to form new memories. Short term memory is important while driving as there is more information needed than just what is being seen. Forgetting the car’s surroundings can cause dangerous situations, as the driver may not realise that there are other cars or other people nearby.

The pre-frontal cortex is used for both planning, as well as self-awareness. This area of the brain is a large part of what differentiates humans from other primates. When the pre-frontal cortex is limited in its ability to function, people make poor decisions for the future. People are also unable to understand how other people interpret their actions, and have difficulty understand their own capabilities. People choosing to drink and drive is often due to their impaired decision making, as well as believing they are more capable than they really are. Accurately understanding the situation at hand is key while driving, as well as predicting what other people will do and planning an appropriate response. Taking unnecessary risks such as overtaking on a blind corner are the causes of many preventable accidents, and alcohol can directly increase the likelihood of people making poor decisions.


Drink driving reaction speeds are effected at levels below alcohol limits

Alcohol inhibits specific functions in the brain, all of which are important while driving. Current neuroscience helps us understand the brain regions that are affected by alcohol, and the subsequent outcomes on driving performance. Even small amounts of alcohol reduce reaction speeds, and as such driving should be avoided even when still legally acceptable under UK drink driving law.

If you are in danger of losing your licence, contact our specialist drink driving solicitors for a free consultation today.