Passive smoking is not healthy, plus I'd trust more on the wheel someone who just drank a glass of beer over someone who just smoked a cannabis joint.
Not to mention the stench of weed smokers...
Not to mention the stench of weed smokers...
Try 6 beers vs 1 entire joint and maybe you're getting somewhere close to equivalence in level of intoxication.
Most people don't smoke an entire joint in one sitting. All it takes is about 3 or 4 puffs and that's typically enough for quite a while. That's the equivalent of about 2 beers. And I'd trust someone more behind the wheel that had a few puffs of a joint vs. someone who just drank 2 or 3 beers.
The kind of intoxication is very different between alcohol and THC. There is no way to do a 1:1 comparison as far as effects on driving ability. They each act on very different pathways, and produce different results.
Marijuana also never made anyone pass out while driving from smoking too much, but alcohol definitely can do that.
For this specific reason, I expect higher variation from weed — though I also wouldn't trust either to drive a car.