When you want to create an open-world, you have to create tools to ease your workflow first. And as I'm still learning and trying my hands at procedural stuff, I just uploaded a video of a procedural system made with Houdini.
Work in progress of my houdini Digital Asset procedural road and railroad using a curve as Input. Still have to fix properly the UVs and some esthethic parameters. Will probably give the .HIP files once done.