i didnt played alot with roads... if not almost none... <abbr title="Colonial Charter">CC</abbr> crew played with it alot more than anyone else...
yes it is 1024x1024 , and i think it is 64x64 per tile. you will want to make some alpha between those lines of 64.
to make ghosted triangle or you do a solid plane which will get moiré alot ... or you can just work with decals and footprints which will only "paint" the ground with your footprint road texture.
like i said, i have almost no experience with roads.