Assign each player a symbol, something you're likely to encounter with regularity on the road, such as the logo of a gas station or fast food restaurant, a bike on a car rack, and so on.
As in the more active version of tag, one player is "It." But in this sit-down game, the It player has to find her symbol, call it out, and (gently) tag another player, who then proceeds to search for his symbol. Play continues ad infinitum -- or until the next bathroom break.