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Representing Road Networks
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Motivation
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  • A great deal is known about the theory of graphs
  • It seems quite natural to represent transportation road networks using graphs
  • But, some important issues arise
A Simple Road Network
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  • Properties:
    • One intersection
    • Four dead ends
    • Four street segments
  • Illustration:
    • images/network1-streets.gif
One Representation
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  • Vertexes/Nodes:
    • The intersection
    • The dead ends
  • Edges/Arcs/Links:
    • The street segments
  • Visualization:
    • images/network1-primal.gif
Limitations of this Representation
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  • Turn restrictions
  • Turn delays
Another Representation
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  • Vertexes/Nodes:
    • The street segments
  • Edges/Arcs/Links:
    • The turning movements
  • Visualization:
    • images/network1-dual.gif
Including Directionality
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The First Representation with Two-Way Streets

images/network1-diprimal.gif
Including Directionality (cont.)
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The Second Representation with Two-Way Streets

images/network1-didual.gif
U-Turns
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One Approach

images/network1-uturnnodes.gif
U-Turns (cont.)
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Another Approach

images/network1-uturnarcs.gif
Origins and Destinations
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  • An Observation:
    • Trips often start from and end at the middle of street segements
  • One Approach:
    • Dummy origin and destination nodes
    • images/dummyod.gif
There's Always More to Learn
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