Traffic accidents: If this is your precedent, why is alcohol legal? Also, most people know when they're stoned better than they know when they're drunk, based on my personal sample of people who both drink and smoke weed.
Public disturbances: No. Pot smokers tend to be quiet, peaceful people, especially when high. Legalization would also reduce some types of crime because people wouldn't have to go out into the streets to get it.
Legal troubles: Well, that's a nebulous ***-cover of a phrase, isn't it? But it's also probably wrong.