Sårbarhetsanalyser av vägnät - gjort sedan förra mötet

1. Sårbarhetsanalyser av vägnät- gjort sedan förra mötet Referensgruppsmöte 18 december 2008

2. Sårbarhetsanalys av utbredda avbrott

3. Background • Past applied vulnerability studies focused on identifying important (critical, significant, vital) links • Our aim: Study vulnerability to area-covering disruptions • Provide complement to single link failure analysis • Develop methodology for systematic analysis • Apply to large real-world road networks • Gain general insights

4. Methodology • Study area is covered with grid of equally shaped and sized cell • Each cell represents spatial extent of disruptive event • Event representation: All links intersecting cell are closed, remaining links unaffected Square Hexagonal

5. Methodology • Multiple, displaced grids used to increase accuracy • Advantages of grid approach: • No coverage bias: Each point in study area equally covered • Avoids combinatioral issues with multiple link failures • Easy to combine with frequency data • Disadvantages: • Results depend on rotation

6. Consequence model • Indicator: Increase in travel time for users • Constant, inelastic travel demand • Initial travel times estimated with congestion, no change during closure

7. Consequence model • During disruption of cell, two possibilities: • No alternative routesUnsatisfied demand, must delay tripuntil after closure • Alternative routesUsers choose new shortest route, or if faster delay trip

8. System and user perspectives • Cell importance: Total increase in travel time for all users when cell is disrupted • Worst-case regional user exposure: Mean increase in travel time per user starting in region when most important cell for region is closed

9. Case study • Swedish road network: 174,044 directed links, 8,764 origins/destinations • Matrix of estimated travel demand (vehicles/hour) between every origin/destination pairPersonal cars and light and heavy trucks • Three square cell sizes: 12.5 km, 25 km, 50 km • 12 hour closure duration

11. Cell importance12.5 km grid

12. Cell importance25 km grid

13. Cell importance50 km grid

14. Cell importance • Unsatisfied demand constitutes 60% - 90% of total increase in travel time on average • Unsatisfied demand consists of internal, inbound/outbound and transit demand • Consequences as function of cell size

15. Jämförelse mellan att stänga hela rutan eller slumpmässigt vald meter väg i rutan • De 11 värsta rutorna finns i Skåne

16. Worst-case county user exposure • Exposure depends on concentrated travel demand, not network redundancy • In most exposed county, more than 60% of demand unsatisfied

17. Worst-casecell vs. link • Area-covering disruption particularly worse in densely populated regions • 12 of 21 counties: Worst-case link within worst-case cell

18. Some insights • Other factors behind vulnerability to area-covering disruptions compared to single link failures • Vulnerability reduced through allocation of restoration resources rather than increasing redundancy • For important cells, unsatisfied demand constitutes nearly all increase in travel time • Results depend on link and demand location and regional partition

19. Sårbarhetsanalys av Mexicos vägnät • Detaljerat (åtminstone bitvis) nätverk (23352 noder, 54172 länkar) • Gles efterfrågematris (ca 500 start/målnoder) • Lastbilsmatris • Mått och metoder från tidigare studier av Sverige

20. Vägnätet

21. Reseefterfrågan

22. Länkarnas betydelsefullhet

23. Delstaternas utsatthet