Ok, some thoughts from when I was with Hikanation, the precursor to the ADT, so a fair amount of road walking.
Aside from just letting your mind wander - as one of my co-hikers who wrote a poem at the end of our hike said:
While sitting in our tiny tents
perhaps we'd learn about this land,
perhaps we'd end up understanding
and comprehending
even more:
our fellow man,
the guy next door.
We'd have occasion to meet them all,
and time share
to spin tales tall
with farmers
or housewives,
or no one at all.
This hike, indeed, had it's greatest wealth
in those moments to be had just by on's self,
eyeing God's beauty,
enjoying the land o'er which we'd walk;
thinking
feeling
having a talk with yourself
on thoughts we'd stored upon the shelf
within our mind
that we never before had time to peruse.
No longer a need to refuse them,
this hike could truly have a reason
in what we might see
both within
and without.
Exerpt from "A Year For Answers" by Stacy Waring
We also sang many of old songs, trying to remember the lyrics, old TV theme songs from our childhood
Since frame packs were the norm, several folks got quite adept at performing as a moving band with recorder, harmonica, and percussion by drumming with sticks on the pack and frame of the person ahead of you.
While road walking, a LOT of folks read novels
I've never really been that bored, even when road walking.