The role of day trips in the first half of the book, when Lucy and the other characters are in Italy, show the way in which characters are changed as a result of the sights that they see and the experiences that happen to them. This is perhaps most obvious when Lucy witnesses a man being killed at the Piazza della Signoria. When the man is stabbed, he looks at Lucy, almost as if he was going to say something to her, but instead only blood came out of his mouth.
Significantly, this incident represents a confrontation between art and life. The narrator in this story shows the importance of this scene in the following quote:
Something happened to the living: they had come to a situation where character tells, and where Childhood enters upon the branching paths of Youth.
There is now no chance for Lucy to return to "the old life" as she puts it. Something has fundamentally changed in her character and she has had her eyes opened to the reality of life and what it entails.
The importance of day trips in this novel therefore is through the way in which they result in important changes in character that will change the course of the characters' lives forever.