I've driven high plenty of times in the past (not anymore though) and the issue is not one of reflexes or judgement, but attention. Being high makes you really

I've driven high plenty of times in the past (not anymore though) and the issue is not one of reflexes or judgement, but attention. Being high makes you really easily distracted, and, in my experience, more likely to take your eyes off the road for longer periods of time. That's where the risk comes from.