It is well established that alcohol impairs one's ability to drive safely. At a blood alcohol concentration of 0.08 per cent (legal permissible level in US), drivers are so impaired that they are 11 times more likely to have a crash than drivers under no influence of alcohol. As per studies carried out in 2006 by National Highway Traffic Safety Administration, US, road traffic accidents under influence of alcohol kill someone every 31 minutes and injure someone every two minutes in US alone. In India, alcohol abuse has been found to be a contributing factor in 30-50 per cent of all road traffic accidents.

Alcohol affects several skills necessary for driving. It only takes low to moderate blood alcohol concentrations (0.03 to 0.05 per cent) to interfere with voluntary eye movements and impair the eyes' ability to rapidly track a moving target. Similarly, at the same concentrations, it affects eye-to-hand reaction time and thus adversely affects steering skills. Alcohol impairs almost every aspect of the brain's information-processing ability and thus alcohol-impaired drivers require more time to read street signs or respond to traffic signals. 

Impairment of the skills related to alcohol increases proportionately to its concentration in the blood stream. The permitted blood alcohol level in India is 0.03 per cent. Though the number of drinks consumed is a poor measure of intoxication, generally the consumption of two standard drinks of alcohol (containing a total of 20 g) by an average sober person will increase the person’s blood alcohol concentration roughly by 0.05 per cent.

The most common method of determining blood alcohol concentration is by measuring the alcohol in an exhaled sample of breath. This is an easy method, which gives results immediately. As per National Committee on Injury Prevention and Control (1989) blood alcohol testing when traffic crashes result in injury is mandatory. In addition, random checking of alcohol levels is done by the road traffic police.

Alcohol affects people differently. Some people can experience signs of impairment at 0.02 per cent whereas others may not experience it until 0.05 per cent. Hence in some countries drivers can be arrested if he is assessed as impaired, even if the blood alcohol concentration is lower than the legal limit. Moreover, there is no evidence of an absolute blood alcohol concentration threshold below which there is no impairment of any kind.

Thus one should definitely avoid driving under the influence of alcohol. The only safe driving limit is 0 per cent.

Pic: Brano Hudak