Representative Routes Discovery from Massive Trajectories

In this work, we study how to find the k most representative routes over large scale trajectory data, which is a fundamental operation that benefits various real-world applications, such as traffic monitoring and public transportation planning. The operator is time-sensitive as it must be able to adapt the results as traffic conditions change. We first prove the NP-hardness of the problem, and then propose a range of effective approximate solutions that have rapid response times. Specifically, we first build a lookup table that stores the trajectories covered by each edge in a given road network. Rather than performing a depth-first search for all possible routes, we find a 1/η approximate solution by developing a maximum-weight algorithm. Since each edge in a route may be close to several trajectories, we further propose a coverage-first algorithm to locate the edges with the greatest coverage gain in the solution route set. By observing that in the real world each edge is connected to only a few other edges in a road network, we have developed a connect-first algorithm that finds consecutive edges for k representative routes by greedily selecting edges with the maximum marginal gain for each route. Finally, comprehensive experiments over two real-world datasets are conducted to verify the effectiveness and efficiency of our proposed algorithms, and provide evidence of the usefulness of our solution and rapid response times in traffic monitoring tasks.