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Redundancy importance: Links as rerouting alternatives during road network disruptions
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.ORCID iD: 0000-0002-4106-3126
2010 (English)In: Procedia Engineering, ISSN 1877-7058, Vol. 3, 129-137 p.Article in journal (Refereed) Published
Abstract [en]

We consider the importance of road links as backup alternatives when other links in the network are disrupted (due to events such as floods, landslides, car accidents etc.). While traditional measures of link importance capture a link’s role for transport efficiency under normal conditions, we are interested in a link’s role for transport robustness and network redundancy. We refer to this concept as redundancy importance and introduce two measures based on traffic flow and disruption impacts (here operationalized as travel delay), respectively. In the flow-based measure we consider the net traffic flow that is redirected to the studied link when other links are closed. In the impact-based measure we also consider the impact that is avoided through the studied link, i.e., how much worse the next-best backup alternatives would be if the studied link itself would not be available. We argue that although a link may not be important under normal conditions, a higher prioritization in resource allocations could be justified if many users could come to rely on it in extraordinary situations. Hence, these measures should be useful as quantitative decision support in the allocation of resources for investments and maintenance as well as for setting up pre-emptive rerouting plans. The measures are applied in a case study of northern Sweden and the general characteristics that determine which links are redundancy important are identified.

Place, publisher, year, edition, pages
2010. Vol. 3, 129-137 p.
Keyword [en]
Network, Vulnerability, Redundancy, Importance, Rerouting, Backup
National Category
Transport Systems and Logistics
URN: urn:nbn:se:kth:diva-24937DOI: 10.1016/j.proeng.2010.07.013ISI: 000282748400012ScopusID: 2-s2.0-78650556729OAI: diva2:354573
1st Conference on Evacuation Modeling and Management
1st Conference on Evacuation Modeling and Management. QC 20101004. QC 20120208Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2012-02-08Bibliographically approved
In thesis
1. Large-Scale Road Network Vulnerability Analysis
Open this publication in new window or tab >>Large-Scale Road Network Vulnerability Analysis
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Disruptions in the transport system can have severe impacts for affected individuals, businesses and the society as a whole. In this research, vulnerability is seen as the risk of unplanned system disruptions, with a focus on large, rare events. Vulnerability analysis aims to provide decision support regarding preventive and restorative actions, ideally as an integrated part of the planning process.The thesis specifically develops the methodology for vulnerability analysis of road networks and considers the effects of suddenly increased travel times and cancelled trips following road link closures. The major part consists of model-based studies of different aspects of vulnerability, in particular the dichotomy of system efficiency and user equity, applied to the Swedish road network. We introduce the concepts of link importance as the overall impact of closing a particular link, and regional exposure as the impact for individuals in a particular region of, e.g., a worst-case or an average-case scenario (Paper I). By construction, a link is important if the normal flow across it is high and/or the alternatives to this link are considerably worse, while a traveller is exposed if a link closure along her normal route is likely and/or the best alternative is considerably worse. Using regression analysis we show that these relationships can be generalized to municipalities and counties, so that geographical variations in vulnerability can be explained by variations in network density and travel patterns (Paper II). The relationship between overall impacts and user disparities are also analyzed for single link closures and is found to be negative, i.e., the most important links also have the most equal distribution of impacts among individuals (Paper III).In addition to links' roles for transport efficiency, the thesis considers their importance as rerouting alternatives when other links are disrupted (Paper IV). Such redundancy-important roads, found often to be running in parallel to highways with heavy traffic, may be warranted a higher standard than their typical use would suggest. We also study the vulnerability of the road network under area-covering disruptions, representing for example flooding, heavy snowfall or forest fires (Paper V). In contrast to single link failures, the impacts of this kind of events are largely determined by the population concentration, more precisely the travel demand within, in and out of the disrupted area itself, while the density of the road network is of small influence. Finally, the thesis approaches the issue of how to value the delays that are incurred by network disruptions and, using an activity-based modelling approach, we illustrate that these delay costs may be considerably higher than the ordinary value of time, in particular during the first few days after the event when travel conditions are uncertain (Paper VI).

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. ix, 45 p.
Trita-TEC-PHD, ISSN 1653-4468 ; 10:005
vulnerability, risk reliability, transport, infrastructure, road network
National Category
Other Social Sciences not elsewhere specified
urn:nbn:se:kth:diva-24952 (URN)978-91-85539-63-5 (ISBN)
Public defence
2010-10-19, D3, Lindstedtsvägen 5, KTH, Stockholm, 13:00 (English)
QC 20101004Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2010-10-04Bibliographically approved

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Jenelius, Erik
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