1. Structural Holes for Structuring Hierarchical Road Network
The 24th International Cartographic Conference
Santiago, Chile ∙ November 15-21, 2009
Structural Holes for Structuring Hierarchical Road Network
Hong Zhang
The Hong Kong Polytechnic University
and
Zhilin Li

2. Outline Why study road network? Review of road network research
Representation and modeling
Properties
Road structure VS human behaviors
Structural holes
Concepts and methodology
Theoretical analysis
Experimental testing
Conclusions

3. Street in the urban system
(a): a Planning city (
(b): Nottingham (
(c): Kevin Lynch “The Image of City”
Urban system vs Human body
Network & Flows vs Blood vessel & blood

4. Street and human life Urban street network  Human behaviors
(a) Navigation (Rosvall et al. 2005)
(b) Traffic flow (Hillier and Iida 2005)
(c) Crime (Nubani and Wineman 2005)
Urban street network  Human behaviors

5. Outline Review of road network research Why study road network?
Representation and modeling
Properties
Road structure VS human behaviors
Structural holes
Concepts and methodology
Theoretical analysis
Experimental testing
Conclusions

6. Representation and Modelling (cont’ed)
Graph
Object
Primal graph
Dual graph
Characteristic
points
Axial line
Stroke
(70 degree)
Named street
Fig. 3: a sample street network of London

7. Representation and Modelling
Graph
Object
Primal graph
Dual graph
ICN
Segment
Alternative
chain
Fig. 3: a sample street network of London

8. Stroke a b c
Natural movement
Deflection angle β α

9. Properties Fractal Small-world Scale-free Self-organized Hierarchical
Fig. 5: Hierarchies emerged from traffic flow distribution (Jiang 2009)

10. Limitations (c) (a) (b)
Fig. 6: (a) the observation windows (Hillier and Iida 2005), (b) Hong Kong (Jiang and Liu 2007) (c) flow dimension and flow capacity (Jiang 2008)

11. Objective
Develop new techniques for
Structuring
Hierarchical road network

12. Outline Structural holes Why study road network?
Review of road network research
Representation and modeling
Properties
Road structure VS human behaviors
Structural holes
Concepts and methodology
Theoretical analysis
Experimental testing
Conclusions

13. Network Science (b) WWW (c) Internet (a) A simple food chain network
nd.edu
300,000 web-pages
(b) WWW
(c) Internet
(d) Protein
(a) A simple food chain network

14. Structural hole and ego network
third
alter
ego
third
alter
ego
third
alter
(a) complete ego-network
(b) ego-control network
(c) ego-passive network
Fig. 8: Three kinds of ego networks

15. Structural hole and ego network
alter1
alter2
ego
alter1
alter2
ego 1
alter1
alter2
ego
(a) complete ego-network
(b) ego-control network
(c) ego-passive network
Fig. 9: Three kinds of ego networks

16. Centrality Rank Proportional Strength Indirect Link Strength
(j∈ine),
(j, q∈ine and q ≠j)
Proportional Strength
Indirect Link Strength
Constraint
Aggregate Constraint
Centrality Rank
alter1
alter2
ego

17. Theoretical illustration
(b) S2
S10
S35
S33
S78
(c)
(d)
Fig. 11: The sampled Road networks and their connectivity graphs

18. Experimental testing (Cont’d)
Fig. 12: The location of Sydost and its road network

19. Experimental testing
Fig. 10: Connectivity graph and traffic flow accommodation of selected roads

20. Conclusions Structural holes can be used for ranking street networks
There is a positive relationship between centrality rank and traffic flow
Weighted link strength and k-step aggregate constraints

21. Acknowledgements
This research is supported by the Hong Kong Polytechnic University and RGC of HK (PolyU5221/07E)
The data about Sydost highway network is provided by Bin Jiang
The San Francisco sampled road network is obtained from TIGER data of U.S.Census Bureau (

22. Thank you！ Questions?