In this mode a lot of traffic cars will spawn all around. Their looks and behavior are pretty simple, but there could be thousands of them.

If you want for cars to work on your track, use a tool Objects Inspector to configure traffic on it first, and then add “traffic-planner-ready” tag to your layout with traffic configured. If you want for track to both be usable online and have traffic, make sure to only leave “ALLOW_NEW_MODE_SCRIPTS=1” in its “surfaces.ini” too, without “ALLOW_TOOLS=1” part (once you’ve done editing). 