When I was a younger man I liked to drive after a litre of vodka.. This was stupid... Just because you can get from point A to B in one piece most of the time drunk, high, tripping, rolling, etc... I had friends get in serious accidents, they are lucky to be alive. It shouldn't be done unless there are significant circumstances. And significant circumstances does not include getting a soda, or a bag, or even driving home most of the time. If one must drive high/drunk stay off the highways, take it slow, because your perception and reaction time are fucked. It also reduces the likely hood that the accident you cause will be life threatening, just don't hit a kid on the street.
Remember your physics class, if not take one, Force = mass * acceleration, Acceleration is the change in velocity over time, a=dv/dt. My car weighs 6000 lbs (2727 kg). So dt = .3038 m / (27 m/s) = 0.01s. The speed then drops from 27 m/s (~60mph) to zero in one foot: a=dv/dt = (27 m/s)/0.01s = 2700 m/s^2. Stay with me... The impact force is f=m*a = 2727 kg * 2700 m/s^2 = 7362900 N or 750807 kg that's 751 metric tons! ouch! if we rework it for 30 mph (14m/s) we get 1758915 N = 17359 kg, only 180 metric tons... so.. about 4 times the impact force. Have I convinced you? If you were your seatbelt it will reduce the impact force felt on people in the car by a factor of about 6, but I don't feel like proving it to you right now.
Just to give you an idea of what 751 metric tons looks like.... its the mass of 8 large dinosaurs (90,000kg), or two 747's at maximum take-off weight (375 metric tons) according to our friends at wolframalpha.
tldr: don't drive drunk, high, or during a religious experience