A speaker walks along a highway through town and passes beneath a bridge with many arches. The poem is short and quiet, and it works mostly through one image: the bridge looks like a cathedral, so an ordinary piece of road becomes something close to sacred.
The first lines say the road is "drinking the light in," as if the highway itself were thirsty. That fits the title, "Dissolute," which usually suggests loose living and excess, though here the drinking feels gentle rather than shameful. Then the speaker goes under the bridge "with sparrow and water / and the poor." Those last words are placed together without comment, so a bird, a stream and poor people all seem to belong to the same shelter.
The speaker feels humble and observant, even a little reverent. The mood is hushed and compassionate, finding a kind of grace in the overlooked parts of a town and in the people who gather there.