Street Network Resilience Put to the Test: The Dramatic Crash of Genoa and Bologna Bridges
2. Literature Review
2.1. Urban Resilience
2.2. Resilience of Urban Form
2.3. Street Network Resilience
2.4. Resilience Indices
3. Materials and Methods
3.1. Angular Segment Analysis
3.2. Street Network Resilience Assessment
4. Street Network Resilience Indices
- Connectivity: presence of road intersections supporting mutual interaction.
- Redundancy: availability of several path alternatives.
- Robustness: road system designed to contain the effect of localised failures.
- Independence: ability to continue operating after a disaster without the need for physical interventions.
- Efficiency: presence of a hierarchic distribution of accessibility levels.
- Diversity: presence of different types of roads with different functions and accessibility levels.
4.1. Mean Connectivity
4.2. Frequency Index
4.3. Synergy Coefficient
4.4. Gini Coefficient
5.1. Case Studies
- Bologna and Genoa are both medium sized cities, with 400,000 and 850,000 inhabitants, respectively.
- During the last century, both cities have grown around their walled historic centres, so as to integrate within a wider conurbation several minor settlements present in their surroundings.
- Both disasters have stricken one of the most congested spatial elements of the road network, namely a bridge ordinarily subjected to crowding due to a continuous and intense vehicular traffic.
- Both bridges belonged to a motorway passing through a metropolitan area.
- The collapse of both bridges provoked a larger crisis affecting the road network system at a national, regional and urban scale.
- In both cases a large part of the traffic flowing in the destroyed motorway sections was originated from vehicles moving from an origin to a destination within the urban area .
5.2. ASA Genoa
5.3. ASA Bologna
5.4. Resilience Assessment
Conflicts of Interest
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|Indicator||Principles||Type||Calculation in a Grid with n Roads||Range|
|Global||Number of connections per node/node count||2 ≤ MC ≤ n|
Choice = Σj Σz fjz(i)/fjz;
fjz(i) = n. of shortest paths between nodes j and z passing through i
fjz = total n. of shortest paths between nodes j and z
|0 ≤ FI ≤ 1|
|Global and Local||R2 coefficient of the linear correlation between:|
Integration Index r800 m
Integration Index rn (r infinity)
|0 ≤ R2 ≤ 1|
|Global||δ = Ac/At |
Ac = concentration area
At = triangular area below line of perfect equality
|0 ≤ δ ≤ 1|
|City and Date||Gini Integration||Gini Choice||Mean Connectivity||Frequency Index||Synergy Coefficient|
|Genoa after ZTL||0.160389||0.86088||3.65581||0.61267||0.53499|
|Genoa before ZTL||0.161179||0.85747||3.65814||0.61544||0.53087|
|Bologna after ZTL||0.122105||0.87817||4.14034||0.37707||0.52900|
|Bologna before ZTL||0.120946||0.87765||4.14276||0.37197||0.52546|
|The configuration of the urban grid is a key component of the resilience of urban form|
|The failure of a central node can seriously impact the global functioning of an organic road network system|
|The configuration of the urban grid influences its capacity to cope with local perturbations|
|Non-physical resilience factors can play a compensating role in the presence of a deficient road network system|
|The proposed configurational approach is a reliable, sustainable planning tool|
|Disaster scenarios can be simulated using the proposed methods to enhance disaster preparedness|
|Disaster impacts can be assessed using the proposed method to estimate the extent and course of network alterations|
|The proposed configurational indices reliably reproduce some key street network resilience properties|
|The method is only valid if supported by an effort to contextualise resilience mapping choices|
|Redundancy of local connections and paths between origin-destination pairs is key for street network resilience|
|Synergy, intended as inner spatial coherence, is key for street network resilience|
|Path polarisation make an urban street network vulnerable to attacks|
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Cutini, V.; Pezzica, C. Street Network Resilience Put to the Test: The Dramatic Crash of Genoa and Bologna Bridges. Sustainability 2020, 12, 4706. https://doi.org/10.3390/su12114706
Cutini V, Pezzica C. Street Network Resilience Put to the Test: The Dramatic Crash of Genoa and Bologna Bridges. Sustainability. 2020; 12(11):4706. https://doi.org/10.3390/su12114706Chicago/Turabian Style
Cutini, Valerio, and Camilla Pezzica. 2020. "Street Network Resilience Put to the Test: The Dramatic Crash of Genoa and Bologna Bridges" Sustainability 12, no. 11: 4706. https://doi.org/10.3390/su12114706