I use to see road traffic. Was very cool to see…especially at night. Traffic coming towards you have white headlights, going away red tail lights. I actually made a flight plan just to fly over I-95 just to see it. This is very easy to do using Little Navmap. Then it just disappeared (the traffic and lights), so I contacted X-Plane Support. They responded “Please try increasing the number of world objects in the graphics settings menu”. That fixed it! Don’t know how it got turned down in the 1st place, but glad it’s back.
