Alcohol could affect your driving by causing:
Impaired vision
Reduced reaction times
Reduced concentration and vigilance
Feeling more relaxed and drowsy, which may cause a driver to fall asleep at the wheel
Difficulty in understanding sensory information
Difficulty doing several tasks at once (e.g. keep in the lane and in the right direction, while concentrating on other traffic)
Failure to obey road rules
Over confidence, which may lead to risk taking