Engineering highway hierarchies

  • Authors:
  • Peter Sanders;Dominik Schultes

  • Affiliations:
  • Karlsruher Institut für Technologie, Karlsruhe, Germany;Technische Hochschule Mittelhessen, Friedberg, Germany

  • Venue:
  • Journal of Experimental Algorithmics (JEA)
  • Year:
  • 2012

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Abstract

Highway hierarchies exploit hierarchical properties inherent in real-world road networks to allow fast and exact point-to-point shortest-path queries. A fast preprocessing routine iteratively performs two steps: First, it removes edges that only appear on shortest paths close to source or target; second, it identifies low-degree nodes and bypasses them by introducing shortcut edges. The resulting hierarchy of highway networks is then used in a Dijkstra-like bidirectional query algorithm to considerably reduce the search space size without losing exactness. The crucial fact is that ‘far away’ from source and target it is sufficient to consider only high-level edges. Experiments with road networks for a continent show that using a preprocessing time of around 15 min, one can achieve a query time of around 1ms on a 2.0GHz AMD Opteron. Highway hierarchies can be combined with goal-directed search, they can be extended to answer many-to-many queries, and they can be used as a basis for other speed-up techniques (e.g., for transit-node routing and highway-node routing).