Lol, no I'm not really a doctor. I'd love to get a PhD someday to make it true, but I'm just a lowly BEng.
What I put is just my own opinion, and the guidelines I follow. In my younger days, I took the guidelines on face value and had a pint after work, driving home immediately. I am slim build and, looking back, I was unfit to drive. I would also go on heavy nights out, stopping at a friends house and driving home the next day. On several occasions I was unfit to drive then, too, although I never thought so at the time.
Now I stick to soft drinks when I have to drive, and am careful about how much I drink if I have to drive the next day. I'm just glad that I did no harm back when I wasn't so careful.