An Efficient Index for Reachability Queries in Public Transport Networks

Mateusz Pawlik, Nikolaus Augsten, Christian S.Jensen, Michael H.Böhlen, Bezaye Tesfaye

Research output: Chapter in Book/Report/Conference proceeding/Legal commentaryConference contributionpeer-review


Computing path queries such as the shortest path in public transport networks is challenging because the path costs between nodes change over time. A reachability query from a node at a given start time on such a network retrieves all points of interest (POIs) that are reachable within a given cost budget. Reachability queries are essential building blocks in many applications, for example, group recommendations, ranking spatial queries, or geomarketing. We propose an efficient solution for reachability queries in public transport networks. Currently, there are two options to solve reachability queries. (1) Execute a modified version of Dijkstra’s algorithm that supports time-dependent edge traversal costs; this solution is slow since it must expand edge by edge and does not use an index. (2) Issue a separate path query for each single POI, i.e., a single reachability query requires answering many path queries. None of these solutions scales to large networks with many POIs. We propose a novel and lightweight reachability index. The key idea is to partition the network into cells. Then, in contrast to other approaches, we expand the network cell by cell. Empirical evaluations on synthetic and real-world networks confirm the efficiency and the effectiveness of our index-based reachability query solution.
Original languageEnglish
Title of host publicationAdvances in Databases and Information Systems
Publication statusPublished - 2020

Fields of Science and Technology Classification 2012

  • 102 Computer Sciences

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