Board Thread:Questions and Answers/@comment-25523075-20161027061326/@comment-28905095-20161027082624

Have you tried using String ? That would lead to 3 block wide roads, and is possibly a little hard to see.

Another option, still 3 blocks wider, could be to use Redstone. This would allow you to connect them together in intersection, and give a rustic feel to the middle line.