PROJECT NUMBER: PSR-26-03

FUNDING SOURCE:

TOTAL COST: $110,000

PERFORMANCE PERIOD: JANUARY 2027 - DECEMBER 2027

Project description

Street networks allow people and goods to move through cities, but disruptions from wildfires, earthquakes, floods, crashes, attacks, construction, or other closures can sever routes and isolate neighborhoods. Planners and MPOs need practical ways to screen street network vulnerability before undertaking costly scenario simulations or project-level engineering studies. Yet the field lacks well-adopted, interpretable measures of network redundancy and chokepoint concentration that can be compared consistently across cities. This project will test whether three simple and intuitive street network indicators predict resilience and robustness outcomes after a network suffers a disruption: link redundancy, length redundancy, and the Gini coefficient of node betweenness centralities. Link redundancy measures how many street segments exist beyond the minimum needed to keep the network connected. Length redundancy measures how much street length exists beyond the minimum-length connected network. Betweenness Gini measures whether shortest-path dependence is spread broadly across the network or concentrated in a small set of chokepoints. The project will use global urban street network models and simulate targeted disruptions to high-centrality nodes, low-elevation flood-style disruptions, and random disruptions. It will model outcomes across increasing levels of network disruption, with particular interpretation for U.S. cities and Southern California. The project responds to urgent regional concerns: Los Angeles-area wildfire evacuations, future earthquakes, flooding, and everyday incident management all depend on street network redundancy and the avoidance of critical chokepoints. The main products will be a peer-reviewed journal article, a PSR final report, a two-page research brief, and documented data and code supporting the findings.