Querying Shortest Paths on Time Dependent Road Networks.

For real-world time dependent road networks (TDRNs), answering shortest path-based route queries and plans in real-time is highly desirable by many industrial applications. Unfortunately, traditional (Dijkstra- or A*-like) algorithms are computationally expensive for such tasks on TDRNs. Naturally, indexes are needed to meet the real-time constraint required by real applications. In this paper, we propose a novel height-balanced tree-structured index, called TD-G-tree, which supports fast route queries over TDRNs. The key idea is to use hierarchical graph partitioning to split a road network into hierarchical partitions. This will produce a balanced tree, where each tree node corresponds to a partition and each parent-child relationship corresponds to a partition and its sub-partition. We then compute and index time dependent shortest paths (TDSPs) only for borders (i.e., vertices whose edges are cut by a partition). Based on TD-G-tree, we devise efficient algorithms to support TDSP queries, as well as time-interval based route planning, for computing optimal solutions through dynamic programming and chronological divide-and-conquer. Extensive experiments on real-world datasets show that our method significantly outperforms existing approaches.