bar ditch

Uncertain. Perhaps from bar + ditch because it ‘bars’ cattle from crossing on to the road; the first word may be a corruption of borrow (compare borrow pit), because the material to make the crown of the road was ‘borrowed’ from the sides.

bar ditch (plural bar ditches)

1. (Southern US) A low ditch running along the side of a road.
   • 2013, Philipp Meyer, The Son, Simon & Schuster, published 2014, page 282:

     She continued along the bar ditch, sweat running down her back now.