Why study road network vulnerability?

1. Road network vulnerability: Identifying important links and exposed regionsErik Jenelius, Tom Petersen, Lars-Göran MattssonDepartment of Transport and Economics, Royal Institute of Technology, Stockholm

2. Why study road network vulnerability? • Reliability and vulnerability important • aspects of transport quality • Efficient commuting • Efficient logistics (just-in-time) • Road network is often a lifeline for other critical • infrastructure • Vulnerability a combination of probability and • consequence • Conditional analysis: Given an adverse event • Which roads are particularly important? • Which regions are particularly exposed?

3. Methodology (1) • Negative event:Link kin a road network is closed • Inelastic travel demand xij • A rural uncongested network • User equilibrium (fastest route) • Travel time for undamaged network • Travel time when link k is closed • Measure of consequence • Unsatisfied demand • Travel time increase

4. Methodology (2) • Importance of link k • Fraction of trips that cannot reach their destinations when it is closed • and (if that fraction is zero  a non-cut link) • Average increase in travel time per trip when it is closed • Worst-case municipality exposure • Fraction of trips with origin in the municipality that cannot reach their destinations when the most important link is closed • and • Average increase in travel time per trip for trips with origin in the municipality when the most important non-cut link is closed

5. Population density Traffic

6. Link importance Fraction of trips that cannot reach their destinations when marked link is closed Average increase in travel time per trip when a non-cut link is closed Links near cities, the coast, or in the mountains Short city links, E4

7. Municipality exposure Fraction of trips that cannot reach their destinations when most important link is closed Average increase in travel time per trip when the most important non-cut link is closed

8. Conclusions • Importance and exposure introduced • to operationalise transport quality • related to reliability and vulnerability • GIS useful way of visualising • results • Importance and exposure should be • considered at various planning stages • Investment: improving and adding links • Maintenance: prioritisation of repair • Operations: prioritisation of snow ploughing

9. Further research • Extend the analysis to the whole of Sweden • Elastic demand: accessibility changes • rather than travel time increases • Application to congested networks • More realistic modelling of adverse events than • just removing one link at a time • Study of probabilities for different adverse • events