Road(s) intersect another road.
Corners are added and the roads are merged to create an intersection.
Road(s) intersect a rail line.
A railway crossing is added at the intersection of the road(s) and the rail line.
Roads intersect another road or rail line, but have different stacking orders.
If the stacking order is larger, the new road forms a viaduct over the older road/rail line.
If the stacking order is lower, the new road forms a tunnel under the older road/rail line.
This also occurs if intersecting roads/rail lines differ in elevation by more than 2½ meters.