RVT to create roads with crossroads

Hi, I have a really simple RVT material to create roads with crooked edges. Basically I have several splines with simple black and white texture (see the image of material) rendered to RVT and this RVT is then used as a mask for the terrain material.

It works good, but the problem is crossroads, where I cannot make it work to looks like proper crossroad. See the image.

This is the road material. Really simple:

Problem is that sometimes the black border from a one spline redraw the while road of another. And I would like to keep the white color there. In other words, place should be white if at least one white part of any road is there.

I tried to sample the RVT to the material, see image below, but nothing changed.

Do you have any idea how I could solve this problem? Thank you very much for answer.