That sounds really safe, especially the bit about not being able to read and comprehend (a stop sign maybe).
As a student I used to see people stoned to varying degrees, I just assumed it was their way of coping with stress and none of my business however when I realised that the driver of the car that I was getting a lift back from a party with was stoned I got out and walked. It was only a couple of miles and much preferred to being a passenger with a driver who was at a much higher risk of not safely arriving at their destination.
Today my opinion hasn't changed, there is no way I want to share the road with a stoned (or drunk or tired) driver, there is enough carnage out there due to bad or slow driver decisions without adding to it.
