kNN Search Utilizing Index of the Minimum Road Travel Time in Time-Dependent Road Networks

Recently, there has been an increasing interest in search in time-dependent road networks where the travel time on roads depends on the time. In such a time-dependent network, the result of k Nearest Neighbor (kNN) queries, which search the k nearest neighbors (kNNs) from the specified location, depends on the query-issuing time. Therefore, existing approaches in static networks are not directly applied for kNN query in time-dependent road networks. In this paper, we propose a kNN search method to achieve a small number of visited vertexes and small response time in time-dependent road networks. In our proposed method, an index structure is constructed based on the minimum travel time on roads in the preprocessing phase. In query processing, a network is expanded by A* algorithm with referring the minimum travel time in the index until kNNs are found. An experimental result shows that our proposed method reduces the number of visited vertexes and the response time compared with an existing method.