Well I took the trip, took notes, and took pictures - and it took over eleven hours to go to the Yankee Smokehouse in Tamworth and back - ordinarily five hours round trip. Finding old routes is harder than I thought. The write-up will take more than one post, but here's a preliminary thought as a Sherlocking followup to Getting Around: the utility poles are a clue as to which is the old main road versus the newer section. There is much more pole variety on those straighter roads that have been put in more recently - which is to say, the 1950's. Sometimes the "new" part of the road has no utility poles at all. There are empty sections of a mile or more, and the wires are already going along the old road quite nicely, so why change them? Or, if it is a built-up section of new road (usually near major intersecting routes), then the utility poles are much newer and the wiring more robust. Both of these make eminent sense. Yet there is a third variety I had never noticed before - slender, uncapped poles that are newer than the old primitive lines, but not especially robust-looking in terms of the amount of electricity they could handle. Route 28 has lots of these sections.
That would never show on a map, of course, but when you're on the ground puzzling over an intersection, the utility poles just lay it out for you where the main road - and hence the road that got numbered - went in 1925: there are poles c. 1925 there. Something else, or nothing, goes up the other road. Obvious once you know it. So that might have been an aid to navigation in the older times with unmarked roads: read the poles.