Basically, commercial vehicles and public buses are allowed to do whatever they want. There is absolutely no line in the sand to cross. Its a free for all.
So, at the risk of sounding like a broken record folks, the buses bellow like jet airplane engines spewing massive amounts of black smoke. The commercial vehicles are appalling, leaving you in a thick cloud. I walked home after work, the pollution is almost dizzying, the noise is beyond comprehension. Not to mention that most cars, especially outside this one city of BA do NOT have mufflers nor are ever inspected. No mufflers, bring a bag of ear plugs if you move here!
Argentina is polluted and noisy and doesnt care!