This paper proposes a K-Main Routes (KMR) approach to summarize spatial network activity. KMR discovers the k shortest paths to cluster activities, generalizing the K-means clustering algorithm for network data. KMR uses network Voronoi diagrams, divide-and-conquer strategies, and pruning to improve performance for applications involving observations along paths in a network, such as locations of pedestrian fatalities. The paper also discusses existing methods like MSGF that can cluster multiple paths, single paths, or no paths, and how KMR aims to improve upon these methods.