Upvote:4
In Rio, there are a bunch of dedicated cycle lanes roughly following the coast, from the old port all the way to Barra. They're easy to recognise, with regularly stamped images of bikes on the road and almost always using red pigment mixed in with the tarmac.
If you're on a road that doesn't have a dedicated cycle lane... you have to use your best judgment.
When cycling in Rio, I stay on the right of the road, sometimes moving onto the sidewalk, depending on how crowded either the road or the sidewalk is.