I believe in 0.37 of Beamng, there was an option to enable Traffic vehicle's visibility on the Minimap in options -> Gameplay -> Traffic. I believe this setting was somewhat buggy, because I distinctly remember it was overriden in some scenarios (Like Garage to Garage). I would love for this feature to come back - Traffic vehicles are hidden by default, and even when you spawn the cars manually in Freeroam (which are by default visible on the Minimap), by starting traffic via the Radial Menu, those manually spawned vehicles become permanently hidden on the "Minimap." The only way I found as a "workaround" to this was by using the UI app "AI Control" and setting each manually spawned vehicle to traffic, but this is both clunky, slow, and doesn't apply to scenarios. Example: I'm driving the D15 Rock Racer (left). Traffic vehicles are spawned via Radial Menu [or scenario] (visible top right), but only my vehicle is shown on the minimap (right). What the minimap used to look like: Traffic vehicles populated the map, and the player was given a distinct arrow separator (this is a screenshot from the Garage To Garage scenario)
I had an old version of Beamng still downloaded, here is the UI menu item I was talking about that is removed in 0.38
