I want to make a road with a bordure as on the picture

[![enter image description here][1]][1]

Currently I do the next steps:

1) 2 main loop cuts vertically, 6 horizontal loop cuts for curving -> 2) Select horizontal edges and manually move each of them to the left -> 3) Additionally, accurate road width by moving vertices -> 4) Select faces and extrude them down 

[![enter image description here][2]][2]

Is there another methods to do this, maybe more accurate/easier? Also, For example, I badly imagine what will I do if need to extend the existing area.

  [1]: https://i.sstatic.net/hOmye.png
  [2]: https://i.sstatic.net/8lU9S.png