This is one of these cases where publication will hardly surprise the reader. Studies of the effect of drinking alcohol upon drivers are unlikely to pronounce that alcohol is safe to take before driving and has no effect on proficiency. The independent variable is alcohol use, the dependent variable is driving ability.
In a 2014 study, it was found, unsurprisingly, that under the influence of alcohol, most drivers tend to be more impulsive and adventurous and their abilities of judgment, vigilance, recognition, reaction, and controlling were impaired. The greater the amount of alcohol, the more reliable the findings. The correlation between drinking, driving and road accidents is nothing new.