It IS an issue.. Too lazy now to search but people have been convicted for drunk driving, having had ONLY ONE DRINK. This is why, going back many years, most people I know say they either drink and not drive, or not drink at ALL and be the designated driver.
However this stupid hare-brained government has got the wrong end of the stick. Not to detract from the seriousness of DUI, the other issue is people driving under the influence of DRUGS, including prescribed medication, which is even worse in some cases than what booze can do.