It may seem obvious but for the safety of others and yourself, sometimes the obvious should be stated. At .08%, the legal limit in Wisconsin, the muscle coordination becomes poor leading to difficulty with balance, speech, vision, reaction time and hearing. It is more difficult to detect danger and a driver’s judgment, self-control, reasoning and memory are impaired. All of this leads to poor concentration, short-term memory loss, speed control, difficulty processing information and impaired perception to a driver under the influence at .08%.
Of course, the more alcohol that is in your system the more diffulties you will encounter in driving safely. However, even at .02% there is a decline in visual functions and a decline in the driver’s ability to perform multiple tasks at the same time.
To learn more about the effects of alcohol, see this breakdown done by the Centers for Disease Control and Prevention: http://www.cdc.gov/Motorvehiclesafety/Impaired_Driving/bac.html.