Jamieson, Fausset and Brown on Deuteronomy 19:3

3. Thou shalt prepare thee a way--The roads leading to them were to be kept in good condition and the brooks or rivers to be spanned by good bridges; the width of the roads was to be thirty-two cubits; and at all the crossroads signposts were to be erected with the words, Mekeleth, Mekeleth, "refuge, refuge," painted on them.

divide the coasts of thy land ... into three parts--the whole extent of the country from the south to the north. The three cities on each side of Jordan were opposite to each other, "as two rows of vines in a vineyard" (see on Jos 20:7).