And both that morning equally lay In leaves no step had trodden black. (11-12)
Our speaker's bias towards the natural world doesn't help him to make his decision after all – when he looks at the roads, he sees that they are worn about the same. Each road seems pretty fresh, because no one has stepped on the newly fallen leaves, turning them black. The image of leaves turning black, which they haven't yet here, is a visual demonstration of how people can destroy the beauty of the natural world.
Two roads diverged in a wood, and I— I took the one less traveled by (18-19)
Though we're not sure if one of the roads actually was less traveled, these lines repeat the speaker's preference for a world less affected by humans. He ends the poem by affirming his choice to take what he thought was the road less traveled, even if it was about equal to the other. It is this affirmative end of the poem that stays with the reader.