As a cyclist, my experience (in the US) is that pedestrians frequently react to a warning of "on your left/right" with a startled, "huh?" reaction, and turn aro

As a cyclist, my experience (in the US) is that pedestrians frequently react to a warning of "on your left/right" with a startled, "huh?" reaction, and turn around to the left to see what's happening. This inevitably puts them in my path, where they weren't before. Unless I'm in a place where people generally understand the concept (shared use recreational bike paths), I don't give an audible warning unless the person is walking erratically, waving their arms as the talk, etc. Broadly speaking, if I want people to keep doing what they're doing so I can pass safely, my experience is that it's better to just pass silently. If I want somebody to alter their behavior so I can pass safely, I'll alert them.