While a few studies have taken driving simulation studies to assess participants with adult attention deficit/hyperactivity disorder and have found them rather impaired to say the least, this one in particular compares the measures to those of controls given drink in which to imbibe. And then gives the ADHD participants drink as well. And all were merry in their driving exploits, with rosy cheeks.
A study under University of Kentucky's J. Weafer et al. (link to the abstract) has found that drivers with ADHD were, somewhat surprisingly, more dangerous sober than control drivers were given alcohol. The effects effectively stacked for alcohol and ADHD.
So will we be cracking down on ADHD drivers anytime soon? Doubtful, but the prospect of the potential for such a crackdown is still unsettling.