Those who followed my studying where old NH Rte 28 went before they put in the new version in the 1950's may remember how fond I am of the tricks for noticing spots where the old routes lay. I found a few on the western half of 101 last summer.
Visiting friends in Elkins, recently, I saw the standard clues of a nearly-parallel side road ending in a built embankment, with the telephone poles running on ahead anyway next to Route 11, which traverses NH east-west in very winding fashion about a third of the way up. I checked the current and older USGS maps at home and sure enough, that road was considerably straightened in the 1950's. Some side sections along the way are even named Old Route 11 - about as nice a confirmation as one could hope for.
Somehow at night in the rain I noticed the sudden disappearance of telephone poles on Route 10 near Marlow, and checked that road as well. That road runs all the way from Connecticut and was called the College Highway well back into the 19th C. I vaguely recalled having heard that years ago. In NH it was called Dartmouth College Road No. 10. I can't find many places where that one has been straightened, according to the map. I had stumbled on one of the few.