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  • 1.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Beyond a complete failure: The impact of partial capacity reductions on public transport network vulnerability2015Conference paper (Refereed)
    Abstract [en]

    Disruptions often result with partial capacity reduction without resulting with a complete breakdown. This study aims to move beyond the analysis of complete failure by investigating the impacts of partial capacity reduction on public transport network performance. We analyse the relation between the extent of capacity reduction at the line level and its consequences on societal costs by performing a full network scan. This analysis framework is applied to planned temporary disruptions in the rapid public transport network in Stockholm, Sweden. Our results indicate that the network is highly vulnerable since it is characterized by greater negative impacts in a disproportional relation to the increase in the original capacity reduction. The non-linear properties of network effects and route choice result in non-trivial relation which carry implications on disruption management the deployment of mitigation measures.

  • 2.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Beyond a complete failure: The impact of partial capacity degradation on public transport network vulnerability2016In: Transportmetrica B: Transport Dynamics, ISSN 2168-0566Article in journal (Refereed)
    Abstract [en]

    Disruptions in public transport networks (PTNs) often lead to partial capacity reductions rather than complete closures. This study aims to move beyond the vulnerability analysis of complete failures by investigating the impacts of a range of capacity reductions on PTN performance. The relation between network performance and the degradation of line or link capacities is investigated by establishing a vulnerability curve and related metrics. The analysis framework is applied to a full-scan analysis of planned temporary line-level capacity reductions and an analysis of unplanned link-level capacity reductions on the most central segments in the multi-modal rapid PTN of Stockholm, Sweden. The impacts of capacity reductions are assessed using a non-equilibrium dynamic public transport operations and assignment model. The nonlinear properties of on-board crowding, denied boarding, network effects and route choice result in non-trivial, generally convex, relations which carry implications on disruption planning and real-time management.

  • 3.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Dynamic Vulnerability Analysis of Public Transport Networks: Mitigation Effects of Real-Time Information2014In: Networks and Spatial Economics, ISSN 1566-113X, E-ISSN 1572-9427, Vol. 14, no 3-4, p. 435-463Article in journal (Refereed)
    Abstract [en]

    In this paper, a dynamic and stochastic notion of public transport network vulnerability is developed. While previous studies have considered only the network topology, the granular nature of services requires a more refined model for supply and demand interactions in order to evaluate the impacts of disruptions. We extend the measures of betweenness centrality (often used to identify potentially important links) and link importance to a dynamic-stochastic setting from the perspectives of both operators and passengers. We also formalize the value of real-time information (RTI) provision for reducing disruption impacts. The developed measures are applied in a case study for the high-frequency public transport network of Stockholm, Sweden. The importance ranking of the links varies depending on the RTI provision scheme. The results suggest that betweenness centrality (passenger/vehicle flows) may not be a good indicator of link importance. The results of the case study reveal that while service disruptions have negative effects and RTI may have significant positive influence, counter examples also exist due to secondary spillover effects.

  • 4.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering. Department of Transport and Planning, Delft University of Technology, Delft, The Netherlands .
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Planning for the Unexpected: The Value of Reserve Capacity for Public Transport Network Robustness2015In: Transportation Research Part A: Policy and Practice, ISSN 0965-8564, E-ISSN 1879-2375, Vol. 81, p. 47-61Article in journal (Refereed)
    Abstract [en]

    Public transport networks (PTN) are subject to recurring service disruptions. Most studies of the robustness of PTN have focused on network topology and considered vulnerability in terms of connectivity reliability. While these studies provide insights on general design principles, there is lack of knowledge concerning the effectiveness of different strategies to reduce the impacts of disruptions. This paper proposes and demonstrates a methodology for evaluating the effectiveness of a strategic increase in capacity on alternative PTN links to mitigate the impact of unexpected network disruptions. The evaluation approach consists of two stages: identifying a set of important links and then for each identified important link, a set of capacity enhancement schemes is evaluated. The proposed method integrates stochastic supply and demand models, dynamic route choice and limited operational capacity. This dynamic agent-based modelling of network performance enables to capture cascading network effects as well as the adaptive redistribution of passenger flows. An application for the rapid PTN of Stockholm, Sweden, demonstrates how the proposed method could be applied to sequentially designed scenarios based on their performance indicators. The method presented in this paper could support policy makers and operators in prioritizing measures to increase network robustness by improving system capacity to absorb unexpected disruptions.

  • 5.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    The impact of reserve capacity on public transport network resilience2013Conference paper (Refereed)
    Abstract [en]

    The resilience of the transport system is acknowledged as an important policy objective. Resilience refers to the extent to which a system is affected by various disturbances, and its capability to recover from such disturbances and restore its level of performance. Public transport networks (PTN) are subject to recurring service disruptions. However, most studies on transport network resilience have focused on the physical degradation of the road network. Hence, their findings have limited transferability to the PTN context. Previous studies on PTN resilience have considered vulnerability in terms of connectivity reliability. Graph theory principles were used to analyze the impact of network structure on robustness with respect to random and intentional attacks. Such analysis allows the comparison of alternative network design properties. However, it does not capture many of the PTN features that we believe are essential for analyzing its resilience.The underlying principles of PTN design and operations make it fundamentally different from road networks and potentially more vulnerable. PTN are usually less dense than the underlying road network, resulting in fewer alternative paths. Moreover, PTN operate close to capacity due to the increasing marginal operation cost during the peak period. In addition, PTN exercise discontinuity in time and space, inducing varying and stochastic waiting, walking and transfer times. Stochastictravel times arise from the inherent and interdependent underlying sources of uncertainty. Another matter thatneeds to be taken into account is that PTN are often multimodal, consisting of several independent infrastructures. As a result of these characteristics, service disruptions in the PTN have wider direct implications compared to the road network due to theescalating impacts on service availability and capacity further downstream. We develop an analysis framework for PTN resilience. The framework integrates stochastic supply and demand models, dynamic route choice and limited operational capacity. Moreover,the plausible correlation between degraded capacities among network elements is captured through the dynamic modellingof network performance. The criticality of a link is evaluated as the increase in system travel time due to a capacity reduction of the link. In general, criticality depends on the flow on the link and the availability of alternative paths in the PTN. We analyze the influence of the capacity of alternative paths on the criticality of a link. High volume to capacity ratios on neighboring links suggest that the effects of the initial disruption can cascade to the surrounding network and lead to severe impacts for many travellers. Further, we analyze the potential of increasing network resilience by increasing capacity on alternative links in response to disruptions. This implies operational strategies such as increasing the frequency on existing lines, or running replacement lines for the disrupted line. This analysis thus enables the evaluation of alternative mitigation measures designed to improve network resilience.

  • 6.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    The value of new cross-radial links for public transport network resilience2014Conference paper (Refereed)
    Abstract [en]

    The introduction of new links to network topology could potentially contrib-ute to greater capability to withstand system breakdowns. This paper analyses the value of adding new cross-radial links for public transport network resilience. The value is evaluated in terms of passenger welfare under disruptions. Using a model that considers passengers’ dynamic travel choices, stochastic traffic conditions, timetables and capacity constraints, a new light rail transit line in Stockholm, Sweden is evaluated. The results show that the cross-radial link reduces the impacts of disrup-tions of critical links; the total value of resilience is positive and significantly offsets the loss in welfare caused by disruption of the cross-radial link itself.

  • 7. Cats, Oded
    et al.
    Jenelius, Erik
    Vulnerability analysis of public transport networks: A dynamic approach and case study for Stockholm2012Conference paper (Refereed)
    Abstract [en]

    In this paper, a dynamic and stochastic notion of public transport network vulnerability is develoepd. While previous studies have considered only the network topology, the non-continuous availability of services requires a more refined model for supply and demand interactions in order to evaluate the impacts of disruptions. We extend the measures of betweenness centrality (often used to identify po-tentially important links) and link importance to a dynamic-stochastic setting from the perspectives of both operators and passengers. We also formalize the value of real-time information (RTI) provision for reducing disruption impacts. The developed measures are applied in a case study for the high-frequency public transport network of Stockholm, Sweden. The importance ranking of the links varies depending on the RTI provision scheme. This suggests that RTI may have significant positive but also negative influence on disruption impacts, and that betweenness centrality (passenger/vehicle flows) may not be a good indicator of link importance.

  • 8. Ding, Jing
    et al.
    Gao, Song
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Rahmani, Mahmood
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Huang, He
    Ma, Long
    Pereira, Francisco
    Ben-Akiva, Moshe
    Routing policy choice set generation in stochastic time-dependent networks: Case studies for Stockholm and Singapore2014Conference paper (Refereed)
    Abstract [en]

    Transportation systems are inherently uncertain due to the occurrence of random disruptions; meanwhile, real-time traveler information offers the potential to help travelers make better route choices under such disruptions. This paper presents the first revealed preference (RP) study of routing policy choice where travelers opt for routing policies instead of fixed paths. A routing policy is defined as a decision rule applied at each link that maps possible realized traffic conditions to decisions on the link to take next. It represents a traveler's ability to look ahead in order to incorporate real-time information not yet available at the time of decision. An efficient algorithm to find the optimal routing policy (ORP) in large-scale networks is presented, as the algorithm is a building block of any routing policy choice set generation method. Two case studies are conducted in Stockholm, Sweden and Singapore, respectively. Data for the underlying stochastic time-dependent network are generated from taxi Global Positioning System (GPS) traces through the methods of map-matching and non-parametric link travel time estimation. The routing policy choice sets are then generated by link elimination and simulation, in which the ORP algorithm is repetitively executed. The generated choice sets are first evaluated based on whether or not they include the observed GPS traces on a specific day, which is defined as coverage. They are then evaluated on the basis of adaptiveness, defined as the capability of a routing policy to be realized as different paths over different days. It is shown that using a combination of link elimination and simulation methods yield satisfactory coverage. The comparison to a path choice set benchmark suggests that a routing policy choice set could potentially provide better coverage and capture the adaptive nature of route choice. The routing policy choice set generation enables the development of a discrete choice model of routing policy choice, which will be explored in the second stage of the study.

  • 9. Ding, Jing
    et al.
    Gao, Song
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Rahmani, Mahmood
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Huang, He
    Ma, Long
    Pereira, Francisco
    Ben-Akiva, Moshe
    Routing Policy Choice Set Generation in Stochastic Time-Dependent Networks Case Studies for Stockholm, Sweden, and Singapore2014In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2466, p. 76-86Article in journal (Refereed)
    Abstract [en]

    Transportation systems are inherently uncertain because of random disruptions; nevertheless, real-time information can help travelers make better route choices under such disruptions. The first revealed-preference study of routing policy choice is presented. A "routing policy" is defined as a decision rule applied at each link that maps possible realized traffic conditions to decisions to be made on the link next. The policy represents a traveler's ability to incorporate real-time information not yet available at the time of decision. Two case studies are conducted in Stockholm, Sweden, and in Singapore. Data for the underlying stochastic time-dependent network are generated from taxi GPS traces through map-matching and nonparametric link travel time estimation. An efficient algorithm to find the optimal touting policy in large-scale networks is first presented, which is a building block of any routing policy choice set generation method. The routing policy choice sets are then generated by link elimination and simulation. The generated choice sets are first evaluated on the basis of whether they include the observed traces on a specific day, or coverage. The sets are then evaluated on the basis of "adaptiveness," defined as the capability of a routing policy to be realized as different paths over different days. A combination of link elimination and simulation methods yields satisfactory coverage. The comparison with a path choice set benchmark also suggests that a routing policy choice set could potentially provide better coverage and capture the adaptive nature of route choice.

  • 10. Ding, Jing
    et al.
    Gao, Song
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Rahmani, Mahmood
    KTH.
    Pereira, Francisco
    Ben-Akiva, Moshe
    Latent-class routing policy choice model with revealed-preference data2015Conference paper (Refereed)
  • 11.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Off-peak goods deliveries in Stockholm inner city - evaluation of transport efficiency2016Conference paper (Other (popular science, discussion, etc.))
  • 12.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Optimal Fleet Selection for Earthmoving Operations2013Conference paper (Refereed)
    Abstract [en]

    Earthmoving operations often involve a large number of specially designed equipment with significant purchasing/leasing prices, high operating and maintenance costs. Hence, choosing the right fleet is a major concern from the construction planners’ point of view. This paper presents a methodology that combines discrete-event simulation and optimization to solve the optimal fleet selection problem for earthmoving operations. Two optimization objectives are formulated and solved using the proposed framework and a genetic algorithm: minimization of Total Cost of Ownership (TCO) and maximization of productivity. Further, a two-stage rating scheme is introduced to arrange the fleet configurations so that the optimization algorithm converges to a fleet with better second-stage performance while the first-stage performance remains at the same level. The case study shows that the proposed mechanism can effectively allocate an optimal equipment combination for earthmoving operations and hence serve as an efficient tool for construction management.

  • 13.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Transport efficiency of off-peak urban goods deliveries: A Stockholm pilot study2017Conference paper (Refereed)
  • 14.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Haris, Koutsopoulos
    Driving time and path generation for heavy construction sites from GPS traces2016In: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, IEEE, 2016, p. 1141-1146Conference paper (Refereed)
    Abstract [en]

    The paper presents a methodology for using GPS probe data to automatically extract the driving time between workstations and build a detailed representation of the paths between workstations in a construction environment. The inferred driving time distribution is aimed as input to construction simulation models to assess fleet performance, while the path information can be utilized to examine the performance of individual vehicles. A case study, using GPS data collected from a construction site, is used to demonstrate the capability of the proposed approach. The GPS data are processed without any prior knowledge about the underlying work environment. The results show that the proposed approach is capable of accurately inferring the driving time distribution and the paths between workstations.

  • 15.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Koutsopoulos, Haris
    Identification of workstations in earthwork operations from vehicle GPS data2016Conference paper (Refereed)
    Abstract [en]

    Increasing availability and the use of Global Positioning System (GPS) devices open great opportunities for various transportation applications. The authors propose a generative probabilistic model for extraction of locations of workstations in earthwork operations using raw GPS traces from construction vehicles. The probabilistic model incorporates the GPS measurements with relevant information extracted from the GPS data to compute locations of different workstations as probability distribution over the environment. The location of workstations will be used as a part of a map inference method for generating and continuously updating the layout and road network topology of the construction environment. A detailed case study was conducted with construction equipment at a complex site. The authors first demonstrate the probabilistic model to extract the locations of loading stations using vehicle speed and interactions among vehicles, and then to discover dumping stations with help of vehicle moving patterns. The results from the experiment show that the proposed method is able to discover important places and workstations for earthwork environment efficiently and in sufficient details.

  • 16.
    Fu, Jiali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering. Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, USA.
    Identification of workstations in earthwork operations from vehicle GPS data2017In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 83, p. 237-246Article in journal (Refereed)
    Abstract [en]

    The paper proposes a methodology for the identification of workstations in earthwork operations based on GPS traces from construction vehicles. The model incorporates relevant information extracted from the GPS data to infer locations of different workstations as probability distributions over the environment. Monitoring of workstation locations may support map inference for generating and continuously updating the layout and road network topology of the construction environment. A case study is conducted at a complex earthwork site in Sweden. The workstation identification methodology is used to infer the locations of loading stations based on vehicle speeds and interactions between vehicles, and the locations of dumping stations based on vehicle turning patterns. The results show that the proposed method is able to identify workstations in the earthwork environment efficiently and in sufficient detail.

  • 17.
    Holmgren, Åke J.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Westin, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Evaluating Strategies for Defending Electric Power Networks against Antagonistic Attacks2007In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 22, no 1, p. 76-84Article in journal (Refereed)
    Abstract [en]

    We show how concepts from game theory can be used to find and evaluate strategies for defending an electric power system against antagonistic attacks. Consequently, the interaction between the antagonist and the defender of the system is envisaged as a game. In a numerical example, we study the performance of different defense strategies against a number of attack scenarios. Particularly, we study whether there is a dominant defense strategy and an optimal allocation of resources between protection of components and recovery.

  • 18.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE).
    Approaches to road network vulnerability analysis2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Incidents in the road transport system can have large negative consequences for the society and the business community. The basic aim of vulnerability analysis is to identify scenarios that i) would lead to severe consequences, and ii) have some likelihood of being realized in the future. The Thesis proposes two main approaches to vulnerability analysis. The first significant component of the analysis is to identify important links in the road network, i.e., links where a disruption would lead to severe consequences. The second component is to identify exposed users, i.e., users for which the consequences of a disruption would be particularly severe.

    Paper I introduces the concepts of importance and exposure and how they can be operationalized in terms of increased travel time when road links are closed. The measures are applied to the road network of northern Sweden. Among other things, we find that the most important road links from a socio-economic efficiency perspective are sections of the main roads in the region going through the main population centres. The most exposed users, on the other hand, live in the sparsely populated municipalities in the northwest along the Norwegian border.

    Paper II studies the geographic patterns of exposure and importance in Sweden and identifies properties of the geography, road network and travel patterns that to a large extent explain the observed spatial differences. We find that the municipalities around Stockholm have the most important road networks, and that people in the southern parts of Sweden are considerably less exposed than in the northern parts. We also find that the sparsity of the road network, the travel times of the users and the traffic load on the links provide good explanatory variables for the regional variations in exposure and importance.

    Paper III proposes a link importance measure that incorporates both efficiency considerations, i.e. the total increase in travel time, and equity considerations, i.e. the unevenness of the distribution among users. We show analytically that there is a strong inverse relationship between the two components. In a case study of the Swedish road network we find that when only efficiency is considered, links in many of the main roads are among the most important. With more weight put on equity, importance is gradually shifted to smaller local roads with poor or no alternative routes.

  • 19.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Considering the user inequity of road network vulnerability2010Report (Other academic)
    Abstract [en]

    An important purpose of the road transport system is to allow people to commute in efficientand reliable ways. For various undesired reasons, however, link capacities are sometimes reduced or linksare closed completely. To assess and reduce the risk of such events, a key issue is to identify road linksthat are particularly important, i.e. roads where disruptions would have particularly severe consequences.This paper presents a method for incorporating user equity considerations into a road link importancemeasure. As a complement to measuring the total increase in vehicle travel time, we also measure thedisparity in the distribution among individual users. These two components are combined to form anequity-weighted importance measure. We study the properties of this measure both analytically and in afull-scale case study of the Swedish road network. A main result is that increasing the weight put on the equity aspect transfers importance from the main roads to smaller local roads. The use of the measure intransport policy and planning is discussed.

  • 20.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Data fusion of instantaneous speeds and point-to-point travel times from probe vehicle data2013Conference paper (Refereed)
  • 21.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Transport and Location Analysis.
    Large-Scale Road Network Vulnerability Analysis2010Doctoral 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).

  • 22.
    Jenelius, Erik
    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.
    Network structure and travel patterns: explaining the geographical disparities of road network vulnerability2009In: Journal of Transport Geography, ISSN 0966-6923, E-ISSN 1873-1236, Vol. 17, no 3, p. 234-244Article in journal (Refereed)
    Abstract [en]

    Inevitably, links in the road network are sometimes disrupted because of adverse weather, technical failures or major accidents. Link closures may have different economic and societal consequences depending on in which regions they occur (regional importance), and users may be affected differently depending on where they travel (regional exposure). In this paper we investigate in what way these geographical disparities depend on the road network structure and travel patterns. We propose aggregate supply-side (link redundancy, network scale, road density, population density) and demand-side (user travel time, traffic load) indicators and combine them in statistical regression models. Using the Swedish road network as a case study, we find that regional importance is largely determined by the network structure and the average traffic load in the region, whereas regional exposure is largely determined by the network structure and the average user travel time. Our findings show that the long-term vulnerability disparities stem from fundamental properties of the transport system and the population densities. Quantitatively, they show how vulnerability depends on different variables, which is of interest for robust network design.

  • 23.
    Jenelius, Erik
    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.
    Redundancy importance: Links as rerouting alternatives during road network disruptions2010In: Procedia Engineering, 2010, Vol. 3, p. 129-137Conference paper (Refereed)
    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.

  • 24.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Road network vulnerability under area-covering disruptions2008In: Young Researchers’ Seminar, 2008Conference paper (Refereed)
  • 25.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Transport and Location Analysis.
    Spatial patterns of road network vulnerability2007In: 9th Nectar Conference, Porto, Portugal, May 9–12, 2007, 2007Conference paper (Refereed)
  • 26.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    The value of travel time variability with trip chains, flexible scheduling and correlated travel times2012In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 46, no 6, p. 762-780Article in journal (Refereed)
    Abstract [en]

    This paper extends the analysis of the value of mean travel time (VMTT) and day-to-day travel time variability (VTTV) from single, isolated trips to daily trip chains, considering the effects of flexibility in activity scheduling and within-day correlation of travel times. Using a multi-stage stochastic programming approach, we show that the VMTT and VTTV on a trip is conditional on the realized travel times on preceding trips, first through the arrival time to the preceding activity and second through the information provided about subsequent travel times. Analytical formulas for the VMTT and VTTV are obtained for two special cases with piecewise constant and linear marginal cost functions, respectively. With flexible scheduling, there is typically a cost associated with a positive correlation of travel times, arising from persistent deviations from typical travel demand or supply on a given day. However, there is also a strict benefit in the dependence since it allows for a more efficient scheduling of later trips.

  • 27.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    User inequity implications of road network vulnerability2010In: Journal of Transport and Land Use, ISSN 1938-7849, Vol. 2, no 3/4, p. 57-73Article in journal (Refereed)
    Abstract [en]

    An important purpose of the road transport system is to allow people to commute in efficientand reliable ways. For various undesired reasons, however, link capacities are sometimes reduced or linksare closed completely. To assess and reduce the risk of such events, a key issue is to identify road linksthat are particularly important, i.e. roads where disruptions would have particularly severe consequences. This paper presents a method for incorporating user equity considerations into a road link importancemeasure. As a complement to measuring the total increase in vehicle travel time, we also measure thedisparity in the distribution among individual users. These two components are combined to form anequity-weighted importance measure. We study the properties of this measure both analytically and in afull-scale case study of the Swedish road network. A main result is that increasing the weight put on theequity aspect transfers importance from the main roads to smaller local roads. The use of the measure intransport policy and planning is discussed.

  • 28.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Vilka regioner är mest sårbara för avbrott i vägnätet och varför?2010Conference paper (Other academic)
  • 29.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Cats, Oded
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    The Value of New Cross-Radial Links for Public Transport Network Robustness2014In: Vulnerability, Uncertainty, and Risk: Quantification, Mitigation, and Management - Proceedings of the 2nd International Conference on Vulnerability and Risk Analysis and Management, ICVRAM 2014 and the 6th International Symposium on Uncertainty Modeling and Analysis, ISUMA 2014, American Society of Civil Engineers (ASCE), 2014, p. 638-647Conference paper (Refereed)
    Abstract [en]

    The introduction of new links to network topology could potentially contribute to greater capability to withstand system breakdowns. This paper analyzes the value of adding new cross-radial links for public transport network robustness. The value is evaluated in terms of passenger welfare under disruptions. Using a model that considers passengers' dynamic travel choices, stochastic traffic conditions, timetables and capacity constraints, a new light rail transit line in Stockholm, Sweden is evaluated. The results show that: (1) the cross-radial link reduces the impacts of disruptions of critical links; and (2) the total value of robustness is positive and significantly offsets the loss in welfare caused by disruption of the cross-radial link itself. © 2014 American Society of Civil Engineers.

  • 30.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Cats, Oded
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    The value of new public transport links for network robustness and redundancy2015In: Transportmetrica A: Transport Science, ISSN 2324-9935, Vol. 11, no 9, p. 819-835Article in journal (Refereed)
    Abstract [en]

    A common argument for introducing new links or services to transport networks is that they will contribute to greater capability to withstand system breakdowns. This paper presents a methodology for assessing the value of new links for public transport network robustness, considering disruptions of other lines and links as well as the new links themselves. The value is evaluated in terms of passenger welfare under disruptions and can be compared to traditional welfare benefits and investment costs. Distinction is made between the value of robustness, defined as the change in welfare during disruption compared to the baseline network, and the value of redundancy, defined as the change in welfare losses due to disruption. The paper introduces the total values of robustness and redundancy by considering a full space of scenarios and their respective frequencies. Using a model that considers passengers' dynamic travel choices, stochastic traffic conditions, timetables and capacity constraints, results are more nuanced than analyses based only on network topology and other static attributes. A new cross-radial light rail transit line in Stockholm, Sweden, is evaluated. The new link increases welfare levels under all scenarios and has a positive value of robustness. However, disruption costs increase under some scenarios and the value of redundancy is negative. In general, the value of redundancy depends on the new link's role as complement or substitute and passengers' ability to utilise spare capacity during short-term unexpected disruptions.

  • 31.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Koutsopoulos, Hans N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Probe vehicle data sampled by time or space: Consistent travel time allocation and estimation2015In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 71, p. 120-137Article in journal (Refereed)
    Abstract [en]

    A characteristic of low frequency probe vehicle data is that vehicles traverse multiple network components (e.g., links) between consecutive position samplings, creating challenges for (i) the allocation of the measured travel time to the traversed components, and (ii) the consistent estimation of component travel time distribution parameters. This paper shows that the solution to these problems depends on whether sampling is based on time (e.g., one report every minute) or space (e.g., one every 500 m). For the special case of segments with uniform space-mean speeds, explicit formulae are derived under both sampling principles for the likelihood of the measurements and the allocation of travel time. It is shown that time-based sampling is biased towards measurements where a disproportionally long time is spent on the last segment. Numerical experiments show that an incorrect likelihood formulation can lead to significantly biased parameter estimates depending on the shapes of the travel time distributions. The analysis reveals that the sampling protocol needs to be considered in travel time estimation using probe vehicle data.

  • 32.
    Jenelius, Erik
    et al.
    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. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Consistent travel time estimation using sparse probe vehicle data sampled by time and distance2012Report (Other academic)
  • 33.
    Jenelius, Erik
    et al.
    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. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Time-based vs. distance-based sampling in probe vehicle data: Implications for travel time estimation2012In: Proceedings of 17th International Conference of Hong Kong Society for Transportation Studies, Hong Kong, 2012Conference paper (Refereed)
    Abstract [en]

    This paper analyses the role of the sampling protocol for travel time estimation with low frequency probe vehicle data by likelihood-based methods, such as maximum likelihood or Bayesian estimation. In the literature, there are reported cases where the vehicle positions are sampled at either certain time intervals, say, every minute, or at certain distance intervals, say, every 500 meters. We show that whether sampling is distance-based or time-based determines the proper formulation of the likelihood function. Furthermore, an incorrect likelihood formulation (for example, treating sampling as distance-based when it is time-based in actuality) often leads to biased parameter estimates. For the special case in which the path is partitioned into segments with constant, independent travel speeds we derive explicit formulas for the likelihood function for each of the two sampling principles. We also study the consistency and bias of the estimators in numerical experiments. 

  • 34.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Travel time estimation for urban road networks using low frequency probe vehicle data2013In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 53, p. 64-81Article in journal (Refereed)
    Abstract [en]

    The paper presents a statistical model for urban road network travel time estimation using vehicle trajectories obtained from low frequency GPS probes as observations, where the vehicles typically cover multiple network links between reports. The network model separates trip travel times into link travel times and intersection delays and allows correlation between travel times on different network links based on a spatial moving average (SMA) structure. The observation model presents a way to estimate the parameters of the network model, including the correlation structure, through low frequency sampling of vehicle traces. Link-specific effects are combined with link attributes (speed limit, functional class, etc.) and trip conditions (day of week, season, weather, etc.) as explanatory variables. The approach captures the underlying factors behind spatial and temporal variations in speeds, which is useful for traffic management, planning and forecasting. The model is estimated using maximum likelihood. The model is applied in a case study for the network of Stockholm, Sweden. Link attributes and trip conditions (including recent snowfall) have significant effects on travel times and there is significant positive correlation between segments. The case study highlights the potential of using sparse probe vehicle data for monitoring the performance of the urban transport system.

  • 35.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Kristoffersson, I.
    Fransson, M.
    Validation of Traffic Simulation Models Based on the Macroscopic Fundamental Diagram2017In: 20th EURO Working Group on Transportation Meeting, EWGT 2017, 4-6 September 2017, Budapest, Hungary, Elsevier, 2017, p. 561-568Conference paper (Refereed)
    Abstract [en]

    Urban traffic simulation models could benefit significantly from new validation methods with potential to reduce the time-consuming calibration and validation work needed before application of the model to evaluate city infrastructure or policy implementations. Current practice is to validate simulation models locally through comparison with point flow measurements and travel times on some important routes. However, for many applications, the level of congestion in an entire area is important. During the last decade, several studies have found empirical evidence of a relation between flow and density on city district level, the existence of a so-called macroscopic fundamental diagram (MFD). This paper shows how the MFD can be used to validate results from a traffic simulation model for a city district. Furthermore, the paper shows empirical results for Stockholm, Sweden.

  • 36.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Kristoffersson, Ida
    Swedish National Road and Transport Research Institute (VTI).
    Fransson, Magnus
    Sweco Society AB.
    Validation of Traffic Simulation Models Based onthe Macroscopic Fundamental Diagram2017Conference paper (Other academic)
    Abstract [en]

    Urban traffic simulation models could benefit significantly from new validation methods with potential to reduce the time-consuming calibration and validation work needed before application of the model to evaluate city infrastructure or policy implementations. Current practice is to validate simulation models locally through comparison with point flow measurements and travel times on some important routes. However, for many applications, the level of congestion in an entire area is important. During the last decade, several studies have found empirical evidence of a relation between flow and density on city district level, the existence of a so-called macroscopic fundamental diagram (MFD). This paper shows how the MFD can be used to validate results from a traffic simulation model for a city district. Furthermore, the paper shows empirical results for Stockholm, Sweden.

  • 37.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Developing a methodology for road network vulnerability analysis2006Conference paper (Refereed)
  • 38.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Road network vulnerability analysis: Conceptualization, implementation and application2015In: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587, Vol. 49, p. 136-147Article in journal (Refereed)
    Abstract [en]

    The paper describes a process for road network vulnerability analysis, from (i) the conceptual definition of vulnerability measures, through (ii) the derivation of practical indicators and models adapted to available data and their implementation in computational procedures, to (iii) the application of the methodology in case studies. In the first step, the vulnerability concept is defined and quantified formally, and distinct user and technological perspectives are highlighted. In the second step, the conceptual measures are adapted and calculated according to the conditions, requirements and goals of a particular analysis. The paper describes practical indicators and algorithms developed for large-scale vulnerability analyses. For the third step, the paper analyzes both single link closures and area-covering disruptions and the distribution of impacts among different regions in a case study on the Swedish road transport system. The spatial patterns are put in connection with the regional variations in location and travel patterns and network density. Finally, the implications for policy and possible approaches to vulnerability management are discussed.

  • 39.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Road network vulnerability analysis of area-covering disruptions: A grid-based approach with case study2010Report (Other academic)
  • 40.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Road network vulnerability analysis of area-covering disruptions: A grid-based approach with case study2012In: Transportation Research Part A: Policy and Practice, ISSN 0965-8564, E-ISSN 1879-2375, Vol. 46, no 5, p. 746-760Article in journal (Refereed)
    Abstract [en]

    We present an approach to systematically analysing the vulnerability of road networks under disruptions covering extended areas. Since various kinds of events including floods, heavy snowfall, storms and wildfires can cause such spatially spread degradations, the analysis method is an important complement to the existing studies of single link failures. The methodology involves covering the study area with grids of uniformly shaped and sized cells, where each cell represents the extent of an event disrupting any intersecting links. We apply the approach to the Swedish road network using travel demand and network data from the Swedish national transport modelling system Sampers. The study shows that the impacts of area-covering disruptions are largely determined by the level of internal, outbound and inbound travel demand of the affected area itself. This is unlike single link failures, where the link flow and the redundancy in the surrounding network determine the impacts. As a result, the vulnerability to spatially spread events shows a markedly different geographical distribution. These findings, which should be universal for most road networks of similar scale, are important in the planning process of resource allocation for mitigation and recovery.

  • 41.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    The impact of network density, travel and location patterns on regional road network vulnerability2010Conference paper (Refereed)
  • 42.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    The vulnerability of road networks under area-covering disruptions2008In: INFORMS Annual Meeting, 2008Conference paper (Refereed)
  • 43.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Levinson, David
    The traveler costs of unplanned transport network disruptions: An activity-based modeling approach2010Conference paper (Refereed)
  • 44.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Levinson, David
    Traveler delay costs and value of time with trip chains, flexible activity scheduling and information2010Report (Other academic)
  • 45.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Levinson, David
    Traveler delay costs and value of time with trip chains, flexible activity scheduling and information2011In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 45, no 5, p. 789-807Article in journal (Refereed)
    Abstract [en]

    The delay costs of traffic disruptions and congestion and the value of travel time reliability are typically evaluated using single trip scheduling models, which treat the trip in isolation of previous and subsequent trips and activities. In practice, however, when activity scheduling to some extent is flexible, the impact of delay on one trip will depend on the actual and predicted travel time on itself as well as other trips, which is important to consider for long-lasting disturbances and when assessing the value of travel information. In this paper we extend the single trip approach into a two trips chain and activity scheduling model. Preferences are represented as marginal activity utility functions that take scheduling flexibility into account. We analytically derive trip timing optimality conditions, the value of travel time and schedule adjustments in response to travel time increases. We show how the single trip models are special cases of the present model and can be generalized to a setting with trip chains and flexible scheduling. We investigate numerically how the delay cost depends on the delay duration and its distribution on different trips during the day, the accuracy of delay prediction and travel information, and the scheduling flexibility of work hours. The extension of the model framework to more complex schedules is discussed.

  • 46.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Petersen, Tom
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Importance and exposure in road network vulnerability analysis2006In: Transportation Research Part A: Policy and Practice, ISSN 0965-8564, E-ISSN 1879-2375, Vol. 40, no 7, p. 537-560Article in journal (Refereed)
    Abstract [en]

    The reliability and vulnerability of critical infrastructures have attracted a lot of attention recently. In order to assess these issues quantitatively, operational measures are needed. Such measures can also be used as guidance to road administrations in their prioritisation of maintenance and repair of roads, as well as for avoiding causing unnecessary disturbances in the planning of roadwork. The concepts of link importance and site exposure are introduced. In this paper, several link importance indices and site exposure indices are derived, based on the increase in generalised travel cost when links are closed. These measures are divided into two groups: one reflecting an "equal opportunities perspective", and the other a "social efficiency perspective". The measures are calculated for the road network of northern Sweden. Results are collected in a GIs for visualisation, and are presented per link and municipality. In view of the recent great interest in complex networks, some topological measures of the road network are also presented.

  • 47.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Petersen, Tom
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Road network vulnerability: Identifying important links and exposed regions2006Conference paper (Refereed)
  • 48.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Rahmani, Mahmood
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Travel time estimation for urban road networks using low frequency GPS probes2012Conference paper (Refereed)
  • 49.
    Jenelius, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Westin, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Holmgren, Åke J.
    Critical infrastructure protection under imperfect attacker perception2010In: International Journal of Critical Infrastructure Protection, ISSN 1874-5482, E-ISSN 2212-2087, Vol. 3, no 1, p. 16-26Article in journal (Refereed)
    Abstract [en]

    This paper considers the problem of allocating finite resources among the elements of a critical infrastructure system in order to protect it from antagonistic attacks. Previous studies have assumed that the attacker has complete information about the utilities associated with attacks on each element. In reality, it is likely that the attacker's perception of the system is not as precise as the defender's, due to geographical separation from the system, secrecy, surveillance, complex system properties, etc. As a result, the attacker's actions may not be those anticipated under the assumption of complete information. We present a modeling framework that incorporates imperfect attacker perception by introducing random observation errors in a previously studied baseline model. We analyze how the perceptive ability affects the attack probabilities and the defender's disutility and optimal resource allocation. We show for example that the optimal resource allocation may differ significantly from the baseline model, that a less perceptive attacker may cause greater disutility for the defender, and that increasing the investment in an element can increase the expected disutility even in a zero-sum situation. 

  • 50. Laskaris, Giorgos
    et al.
    Cats, Oded
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Viti, Francesco
    A real-time holding decision rule accounting for passenger travel cost2016In: 2016 IEEE International Conference on Intelligent Transportation Systems (ITSC), IEEE conference proceedings, 2016, p. 2410-2415Conference paper (Refereed)
    Abstract [en]

    Holding has been extensively investigated as a strategy to mitigate the inherently stochastic nature of public transport operations. Holding focuses on either regulating vehicle headways using a rule-based approach or minimizing passenger travel cost by employing optimization models. This paper introduces a holding decision rule that explicitly addresses passenger travel cost. The decision to hold relies on the passenger demand distribution along the line. The passenger cost holding rule is tested using simulation for a high frequency bus line in Stockholm, Sweden and is compared with a no-control scheme and the currently used headway-based strategy. The results indicate that the new decision rule results in relatively minor reductions of passenger cost compared to the currently adopted strategy, and that it allocates the greatest share of holding time at the beginning of the route.

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