The highways were happy because the poet was happy when he traveled them. The happiness of the highways is connected to the poet's emotions and experiences while traveling on them. The poet's positive feelings and memories associated with the highways are reflected in the idea of the highways themselves being happy. This personification of the highways conveys the sense of joy and contentment the poet felt during their journeys.
In poetry, such symbolic and metaphorical expressions are often used to convey deeper emotions and experiences. By attributing human emotions like happiness to inanimate objects like highways, the poet creates a vivid and imaginative image that enriches the meaning of the poem. The happiness of the highways serves as a reflection of the poet's own happiness and the positive moments shared with these roads during their travels.
