Help creating these types of curved roads and then applying perfect textures

FireNoodle

Sorry if this is the wrong section, first post here. 

I'm trying to create these curved bits, and then apply the materials? How do they get perfect degree turns and square textures on top of that? And how would I go about doing this in the unreal engine? I was thinking some sort of paths, and then the 'stone textures' on the right are part of the landscape? So painting perfectly straight textures, somehow with an alpha or something. The rest on the ground are decals im guessing. 

The curved bits might be one modular piece, and then it's just stretched out? I dunno.

gnoop

Isn't it obvious , you insert a polygon stripe for the curbs  and pit a narrow tiling along  texture there.   Or maybe I just don't get the issue.  Manholes are decals, stones is another insertion .   Dusty corners are one more texture layer  based on AO  or vertex color mask or maybe just decals too

Obscura

You unwrap those curved meshes to a straight shape so you can tile a texture along it. The road parts that you marked are inserted polygons.

poopipe

The paved parts are a separate material mapped top down in world space which gets around problems with distortion caused by unfolding the kerbs etc. straight