In the UK they test for drink, cannabis and cocaine if you are involved in a road accident, or if your car stinks of puff on a stop...
So in the UK at least, they have done the research on what actually does to your brain cells and the operation of a motor vehicle...
Plus, puff stays in your system waaay longer than the effects of beer, beer is dealt with in a few hours, but puff, read below.
https://www.healthline.com/health/how-long-does-weed-stay-in-your-system