Most numbered roads and some of the others (Ball Hill, Brook Station, Mountain, Leominster) have old county layout markers (granite square posts) which are marked WCH. These mark the edge of the Town’s property.
The way roads were measured back in the day were by rods. One rod is 16.5 feet long. Most secondary roads are 2 rods (33 feet) wide.
Note that the width of a road can vary along its length.
Consult the Highway Department for an exact width if you are concerned about setbacks or ownership of a tree.