THE APPEAL OF the road trip, or the long through-hike, or the pilgrimage, is that the ‘‘point’’ is so deliberately minimal — to arrive at, you know, the end — and the decisions involved so banal (stop for gas now, or in a bit?) that the distinction between signal and noise is blurred. The point of a photograph of a trail, or some billboard half-seen out the window of a bus, is that it could easily be exchanged for the image taken immediately before or immediately afterward. The random sample communicates in one unpremeditated frame all the significance that particular person’s drive down that particular road could possibly contain. This is the aspiration common to road-trip literature and road-trip photography: The moment at the gas station is held, insistently, to express as much about the total experience as the shot of the Eiffel Tower.