1 Road network vulnerability: Identifying important links and exposed regions Erik Jenelius, Tom Petersen, Lars-Göran Mattsson Department 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 k in a road network is closed Inelastic travel demand x ij 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 Fraction of trips that cannot reach their destinations when marked link is closed Link importance 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