Marijuana is a hallucinogen, thusly making it more dangerous than alcohol. (Alcohol is bad, it's a depressant, but thinking the other car was a cookie and wanting it would probably be worse). Marijuana is also FAR worse for your lungs than cigarettes.
The British Lung Foundation studied this, and reported:
"According to the study, smoking three marijuana cigarettes a day can cause the same damage as 20 cigarettes. And those who smoke both marijuana and cigarettes are further increasing their risk of lung damage."