MASH 2015 - Bombing the hills of SF with colored smoke

I always wondered what the legal criteria was for pulling a stunt like this. I mean, technically, it's gotta be a road hazard right? I've thought about doing something like this before especially since Enola Gaye smoke grenades are so easily had and cheap. For those who have never used these, they last for about 2 minutes before going caput. Maybe I should get some of these for camping.