Anybody who's smoked a lot of weed knows that THC tolerance works very differently from alcohol tolerance. If you've been ripping dabs every couple hours for the last month, you might be well above the legal limit and barely feel different at all. On the other hand, if you haven't smoked in a year and take a single hit of a modern joint, you could be floored.

I'm not sure how THC intoxication could be measured, but blood THC concentration feels like an incredibly crude metric compared to BAC.

Smoking weed is terrible for you. Either drink or do psychedelics.