The road materials "sort bias" parameter (0-7) determines if roads are layered on top or below other roads.

Currently, it is 1 for all asphalt road materials and 0 for all dirt roads and trails - except for Dirt_01, which is 1 for some reason.

Making proper use of this feature would allow for better road sorting, which is also useful for terrain modders.

Here are some recommended values: 0 for trails, 2 for dirt roads, 4 for minor asphalt roads and 6 for major asphalt roads.