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  • 51.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Bierlaire, Michel
    Metropolis-Hastings sampling of paths2011Report (Other academic)
    Abstract [en]

    We consider the previously unsolved problem of sampling cycle-free pathsaccording to a given distribution from a general network. The problem isdifficult because of the combinatorial number of alternatives, which prohibitsa complete enumeration of all paths and hence also forbids to computethe normalizing constant of the sampling distribution. The problemis important because the ability to sample from a known distribution introducesmathematical rigor into many applications that range from routeguidance to the estimation of choice models with sampling of alternatives.

  • 52.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Bierlaire, Michel
    Running urban microsimulations consistently with real-world data2011In: Digital Urban Modelling and Simulation / [ed] S. Müller Arisona, G. Aschwanden, J. Halatsch, Springer, 2011Chapter in book (Other academic)
  • 53.
    Flötteröd, Gunnar
    et al.
    École Polytechnique Fédérale de Lausanne (EFPL), School of Architecture, Civil and Environmental Engineering (ENAC), Lausanne, Switzerland.
    Bierlaire, Michel
    Nagel, Kai
    Bayesian demand calibration for dynamic traffic simulations2011In: Transportation Science, ISSN 0041-1655, E-ISSN 1526-5447, Vol. 45, no 4, p. 541-561Article in journal (Refereed)
    Abstract [en]

    We present an operational framework for the calibration of demand models for dynamic traffic simulations, where calibration refers to the estimation of a structurally predefined model's parameters from real data. Our focus is on disaggregate simulators that represent every traveler individually. We calibrate, also at an individual level, arbitrary choice dimensions within a Bayesian framework, where the analyst's prior knowledge is represented by the dynamic traffic simulator itself and the measurements are comprised of time-dependent traffic counts. The approach is equally applicable to an equilibrium-based planning model and to a telematics model of spontaneous and imperfectly informed drivers. It is based on consistent mathematical arguments, yet it is applicable in a purely simulation-based environment and, as our experimental results show, is capable of handling large scenarios.

  • 54.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory (TRANSP-OR), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Chen, Yu
    Nagel, Kai
    Behavioral calibration and analysis of a large-scale travel microsimulation2012In: Networks and Spatial Economics, ISSN 1566-113X, E-ISSN 1572-9427, Vol. 12, no 4, p. 481-502Article in journal (Refereed)
    Abstract [en]

    This article reports on the calibration and analysis of a fully disaggregate (agent-based) transport simulation for the metropolitan area of Zurich. The agent-based simulation goes beyond traditional transport models in that it equilibrates not only route choice but all-day travel behavior, including departure time choice and mode choice. Previous work has shown that the application of a novel calibration technique that adjusts all choice dimensions at once from traffic counts yields cross-validation results that are competitive with any state-of-the-art four-step model. While the previous study aims at a methodological illustration of the calibration method, this work focuses on the real-world scenario, and it elaborates on the usefulness of the obtained results for further demand analysis purposes.

  • 55.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Chen, Yu
    Berlin Institute of Technology, Transport Systems Planning and Transport Telematics Laboratory.
    Nagel, Kai
    Berlin Institute of Technology, Transport Systems Planning and Transport Telematics Laboratory.
    Choice Model Refinement from Network Data2012Conference paper (Refereed)
  • 56.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Chen, Yu
    Rieser, Marcel
    Nagel, Kai
    Behavioral calibration of a large-scale travel behavior microsimulation2009In: Proceedings of the 12th International Conference on Travel Behaviour Research, 2009Conference paper (Refereed)
  • 57.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Gattami, Ather
    Capturing stochasticity in traffic networks for robust ITS applications2012Conference paper (Refereed)
  • 58.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Liu, Ronghui
    Disaggregate path flow estimation in an iterated DTA microsimulation2011Conference paper (Other academic)
  • 59.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Liu, Ronghui
    Disaggregate path flow estimation in an iterated DTA microsimulation2010Report (Other academic)
    Abstract [en]

    This text describes the first application of a novel path flow and origin/destination(OD) matrix estimator for iterated dynamic traffic assignment (DTA) microsimulations.The presented approach, which operates on a trip-based demand representation,is derived from an agent-based DTA calibration methodology that relies onan activity-based demand model. The objective of this work is to demonstrate thetransferability of the agent-based approach to the more widely used OD matrixbaseddemand representation.The calibration (i) operates at the same disaggregate level as the microsimulationand (ii) has drastic computational advantages over usual OD matrix estimators inthat the demand adjustments are conducted within the iterative loop of the DTAmicrosimulation, which results in a running time of the calibration that is in thesame order of magnitude as a plain simulation. We describe an application ofthis methodology to the trip-based DRACULA microsimulation and present anillustrative example that clarifies its capabilities.

  • 60.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Liu, Ronghui
    Disaggregate Path Flow Estimation in an Iterated Dynamic Traffic Assignment Microsimulation2014In: Journal of Intelligent Transportation Systems / Taylor & Francis, ISSN 1547-2450, E-ISSN 1547-2442, Vol. 18, no 2, p. 204-214Article in journal (Refereed)
    Abstract [en]

    This article describes the first application of a novel path flow and origin/destination (OD) matrix estimator for iterated dynamic traffic assignment (DTA) microsimulations. The presented approach, which operates on a trip-based demand representation, is derived from an agent-based DTA calibration methodology that relies on an activity-based demand model (Flotterod, Bierlaire, & Nagel, 2011). The objective of this work is to demonstrate the transferability of the agent-based approach to the more widely used OD matrix-based demand representation. The calibration (i) operates at the same disaggregate level as the microsimulation and (ii) has drastic computational advantages over conventional OD matrix estimators in that the demand adjustments are conducted within the iterative loop of the DTA microsimulation, which results in a running time of the calibration that is in the same order of magnitude as a plain simulation. We describe an application of this methodology to the trip-based DRACULA microsimulation and present an illustrative example that clarifies its capabilities.

  • 61.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Lämmel, Gregor
    Bidirectional pedestrian fundamental diagram2015In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 71, p. 194-212Article in journal (Refereed)
    Abstract [en]

    This article presents a new model of stationary bidirectional pedestrian flow. Starting out from microscopic first principles, a bidirectional fundamental diagram (FD) is derived that defines direction-specific flow rates as functions of direction-specific densities. The FD yields non-negative and bounded flows and guarantees that the instantaneous density changes that would result from these flows stay bounded between zero and jam density. In its minimal configuration, it uses just as many parameters as a unidirectional triangular FD: maximum walking speed, jam density, a collision avoidance parameter (from which the backward wave speed can be derived). A one-on-one mapping between the parameters guiding uni- and bidirectional pedestrian flows is proposed and both conceptually and empirically justified. Generalizations of the FD that maintain its desirable properties turn out to be straightforward by making its parameters density-dependent. The FD performs very well in comparisons against simulated and real data.

  • 62.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Lämmel, Gregor
    Evacuation simulation with limited capacity sinks2010In: Proceedings of the International Conference on Evolutionary Computation, Valencia, Spain, 2010, p. 249-254Conference paper (Refereed)
    Abstract [en]

    We heuristically solve an evacuation problem with limited capacity shelters. An evolutionary learning al gorithm is developed for the combined route- and shelter-assignment problem. It is complemented with a heuristic method for the fair minimization of shelter capacities. Different behavioral assumptions "fair" vs. "globally optimal") are investigated. The proposed approaches are discussed in the context of a real-world tsunami evacuation problem.

  • 63.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Meijer, Sebastiaan
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Gaming simulations with environmental trajectories that maximize information gain2012In: Proceedings of the 2012 Winter Simulation Conference (WSC), IEEE , 2012, p. 6465068-Conference paper (Refereed)
    Abstract [en]

    Gaming simulations put real actors in simulated environments. Example applications are training and scenario analysis in transport operations and disaster management. Running a single gaming simulation is an expensive endeavor and therefore must be led through interesting scenario configurations to maximize the learning or research outcomes. This article presents an approach to automatically control the simulated environment in account for the real players' behavior such that a maximum usability of the session is ensured. The approach accesses elements from discrete choice theory and provides the game designer with different options to tailor the type of learning. An archetypical application demonstrates the usefulness of the approach.

  • 64.
    Flötteröd, Gunnar
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Nagel, Kai
    Behavioral dimensions in transport microsimulations2010Report (Other academic)
  • 65.
    Flötteröd, Gunnar
    et al.
    Group for Transport Systems Planning and Transport Telematics, Technische Universität Berlin.
    Nagel, Kai
    High-speed combined micro/macro simulation of traffic flow2007In: 2007 IEEE INTELLIGENT TRANSPORTATION SYSTEMS CONFERENCE, Seattle, USA, 2007, p. 926-931Conference paper (Refereed)
    Abstract [en]

    We describe two new and practically relevant simulation techniques related to the Kinematic Wave Model of traffic flow. Firstly, we demonstrate how the well-known Godunov solution scheme can be run on variable time scales in a computationally very efficient way. Secondly, we demonstrate how the resulting macroscopic traffic flow model can be run in conjunction with a microscopic model of driver behavior while maintaining high computational performance.

  • 66.
    Flötteröd, Gunnar
    et al.
    Group for Transport Systems Planning and Transport Telematics, Technische Universität Berlin.
    Nagel, Kai
    Modeling and estimation of combined route and activity location choice2006In: Proceedings of the 9th IEEE Intelligent Transportation Systems Conference, Toronto, Canada, 2006, p. 394-399Conference paper (Refereed)
    Abstract [en]

    This article describes a behavioral model of combined route and activity location choice. The model can be simulated by a combination of a time variant best path algorithm and dynamic programming, yielding a behavioral pattern that minimizes a traveler's perceived cost. Furthermore, the model is extended in a Bayesian manner, providing behavioral probabilities not only based on subjective costs, but also allowing for the incorporation of anonymous traffic measurements and the formulation of a traffic state estimation problem, which can efficiently be solved by an available algorithm.

  • 67.
    Flötteröd, Gunnar
    et al.
    Transport Systems Planning and Transport Telematics Laboratory, Technical University of Berlin, Germany.
    Nagel, Kai
    Online traffic state estimation with multi-agent simulations2008In: Proceedings of the 4th International Symposium Networks for Mobility, 2008Conference paper (Refereed)
    Abstract [en]

    This article describes a novel approach to online traffic state estimation with multi-agent simulations. The presented method identifies individual-level motorist behavior from aggregate measurements of flows, densities or velocities that are obtained at a limited set of network locations. Behavioral dimensions that can be estimated range from single route choice to the selection of full-day plans. The estimation logic only requires a simulation-based representation of the behavioral dimensions under consideration in order to simulate the most plausible driver behavior given the additional information contained in the sensor data. No mathematical description of the behavioral driver model is needed such that the broad modeling capabilities of a multi-agent simulation can be fully exploited.

  • 68.
    Flötteröd, Gunnar
    et al.
    Transport Systems Planning and Transport Telematics Laboratory, Technical University of Berlin, Germany.
    Nagel, Kai
    Simulation and optimization of trajectories in a congested network2006Report (Other academic)
    Abstract [en]

    The subject of this article is twofold. Firstly itdescribes how a dynamic macroscopic network loading modelcan be used to simulate the movement of arbitrarily complexindividual particles (agents) through a network without loss ofthe macroscopic model’s differentiability. Based on this resultthe problem of minimizing a given functional of the macroscopicmodel’s states by adjustment of individual agents’ trajectoriesis considered. A solution procedure is proposed, which is basedon subsequent linearizations of the overall system dynamics andtime variant best path calculations.

  • 69.
    Flötteröd, Gunnar
    et al.
    Group for Transport Systems Planning and Transport Telematics, Technische Universität Berlin.
    Nagel, Kai
    Some practical extensions to the cell transmission model2005In: 2005 IEEE Intelligent Transportation Systems Conference (ITSC), Vienna, Austria, 2005, p. 172-177Conference paper (Refereed)
    Abstract [en]

    This article describes some practical extensions to Daganzo's Cell Transmission Model. Flow calculations for straight, merge, and diverge cells are subsumed in a single computation scheme which allows for arbitrary cell connectivity. Since it is planned to apply the resulting model in a mathematical programming based traffic monitoring system, approximate sensitivities are also provided.

  • 70.
    Flötteröd, Gunnar
    et al.
    Transport Systems Planning and Transport Telematics Laboratory, Technical University of Berlin, Germany.
    Nagel, Kai
    State estimation for multi-agent simulations of traffic2007In: Proceedings of the 2007 World Conference on Transport Research, 2007Conference paper (Refereed)
    Abstract [en]

    This article describes a novel method for microsimulation-based traffic stateestimation, which adjusts individual travelers' route and activity location choiceto anonymous measurements e.g. of flows or velocities. While a discussion ofthe algorithm's rather mathematical functioning is omitted, the approach isclarified by means of an illustrative example. A second example of realistic sizeunderlines the method's real world applicability and its real time capabilities.

  • 71.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Osorio, C.
    Stochastic network link transmission model2017In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 102, p. 180-209Article in journal (Refereed)
    Abstract [en]

    This article considers the stochastic modeling of vehicular network flows, including the analytical approximation of joint queue-length distributions. The article presents two main methodological contributions. First, it proposes a tractable network model for finite space capacity Markovian queueing networks. This methodology decomposes a general topology queueing network into a set of overlapping subnetworks and approximates the transient joint queue-length distribution of each subnetwork. The subnetwork overlap allows to approximate stochastic dependencies across multiple subnetworks with a complexity that is linear in the number of subnetworks. Additionally, the network model maintains mutually consistent overlapping subnetwork distributions. Second, a stochastic network link transmission model (SLTM) is formulated that builds on the proposed queueing network decomposition and on the stochastic single-link model of Osorio and Flötteröd (2015). The SLTM represents each direction of a road and each road intersection as one queueing subnetwork. Three experiments are presented. First, the analytical approximations of the queueing-theoretical model are validated against simulation-based estimates. An experiment with intricate traffic dynamics and multi-modal joint distributions is studied. The analytical model captures most dependency structure and approximates well the simulated network dynamics and joint distributions. Even for the considered simple network, which consists of only eight links, the proposed subnetwork decomposition yields significant gains in computational efficiency: It uses less than 0.0025% of the memory that is required by the use of a full network model. Second and third, the proposed SLTM is illustrated with a linear test network adopted from the literature and a more general topology network containing a diverge node and a merge node. Time-dependent probabilistic performance measures (occupancy uncertainty bands, spillback probabilities) are presented and discussed.

  • 72.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Osorio, Carolina
    Analytical modeling of dynamic stochastic network flows2012Conference paper (Refereed)
  • 73.
    Flötteröd, Gunnar
    et al.
    Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Transport and Mobility Laboratory (TRANSP-OR), Lausanne, Switzerland.
    Rohde, Jannis
    Operational macroscopic modeling of complex urban road intersections2011In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 45, no 6, p. 903-922Article in journal (Refereed)
    Abstract [en]

    This article describes a new approach to the macroscopic first order modeling and simulation of traffic flow in complex urban road intersections. The framework is theoretically sound, operational, and comprises a large body of models presented so far in the literature.

    Working within the generic node model class of Tampere et al. (2011), the approach is developed in two steps. First, building on the incremental transfer principle of Daganzo et al. (1997), an incremental node model for general road intersections is developed. A limitation of this model (as of the original incremental transfer principle) is that it does not capture situations where the increase of one flow decreases another flow, e.g., due to conflicts. In a second step, the new model is therefore supplemented with the capability to describe such situations. A fixed-point formulation of the enhanced model is given, solution existence and uniqueness are investigated, and two solution algorithms are developed. The feasibility and realism of the new approach is demonstrated through a synthetic and a real case study.

  • 74.
    Flötteröd, Gunnar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Wagner, Peter
    Flötteröd, Yun-Pang
    Identifiability and Practical Relevance of Complex Car-Following Models2013In: Traffic and Granular Flow '11, Springer, 2013, p. 47-55Conference paper (Other academic)
    Abstract [en]

    This article looks at car-following models from a deliberately pragmaticperspective: What information about driver behavior can be extracted from a givendata set without more or less speculative assumptions about underlying behaviorallaws? The objective of this exercise is not to invalidate existing models but toobtain a better understanding of how much (complex) model structure can berevealed/validated from real data.

  • 75. Flügel, Stefan
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Kwong, C.K.
    Steinsland, C.
    Evaluation of methods for calculating traffic assignment and travel times in congested urban areas with strategic transport models2014Report (Other (popular science, discussion, etc.))
  • 76. Himpe, Willem
    et al.
    Flötteröd, Gunnar
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Bierlaire, Michel
    Hurtubia, Ricardo
    Modeling the dynamics of all-day activity plans2010Conference paper (Other academic)
  • 77. Huibregtse, Olga
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Bierlaire, Michel
    Hegyi, Andreas
    Hoogendoorn, Serge
    A fixed-point approach to system-optimal route advice considering compliance behavior2012In: Proceedings of the Annual Meeting of the Transportation Research Board, Washington DC, USA, 2012Conference paper (Refereed)
  • 78. Huibregtse, Olga
    et al.
    Flötteröd, Gunnar
    Bierlaire, Michel
    Hegyi, Andreas
    Hoogendoorn, Serge
    Optimization of evacuation instructions as a fixed-point problem.2011In: Proceedings of the Swiss Transport Research Conference (STRC), Monte Verita/Ascona, Switzerland, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper, a new framework is presented to optimize evacuation instructions. By giving optimized instructions to the evacuees (for example about which route to take), traffic conditions and, therefore, the evacuation efficiency are optimized. To solve the problem in an efficient way, the problem is decomposed into three simpler problems, namely the optimization of turning fractions, the optimization of instructions given the turning fractions, and the approximation of compliance behavior. Mutual consistency of these sub-problems is enforced through a fixed-point formulation.

  • 79. Hurtubia, Ricardo
    et al.
    Flötteröd, Gunnar
    Ecole Polytech Fed Lausanne.
    Bierlaire, Michel
    Ecole Polytech Fed Lausanne.
    Estimation techniques for MEV models with sampling of alternatives2010In: Proceedings of the European Transport Conference, Glasgow, Scotland, 2010Conference paper (Refereed)
    Abstract [en]

    Estimation of MEV models with large choice sets requires sampling of alternatives, which might be a difficult task due to the correlated-structure of the error terms. Standard sampling techniques like the ones traditionally used for Multinomial Logit models cannot be directly applied in the estimation of more complex MEV models. State of the art estimators for MEV models with sampling of alternatives either require knowledge of the full choice set or produce biased estimates for small sample sizes.This paper proposes two estimation techniques for MEV models with sampling of alternatives. The first technique is based on bootstrapping and allows to reduce the bias for existing estimators. A Monte Carlo simulation experiment is performed to show how this technique reduce the bias of a state-of the-art estimator for a Nested Logit model considering sampling of alternatives. The second technique introduces a new estimator, based on importance sampling of alternatives . A second Monte Carlo experiment is performed to compare this estimator with the current state of the art. The proposed estimator generates unbiased parameter estimates for a Nested Logit model considering small sample sizes. The techniques can be easily applied to other members of the MEV family of models, like the Cross-Nested Logit.

  • 80. Hurtubia, Ricardo
    et al.
    Flötteröd, Gunnar
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne.
    Bierlaire, Michel
    Inferring the activities of smartphone users from context measurements using Bayesian inference and random utility models2009In: Proceedings of the European Transport Conference, The Netherlands, 2009Conference paper (Refereed)
  • 81. Hurtubia, Ricardo
    et al.
    Martìnez, Francisco
    Flötteröd, Gunnar
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne.
    Bierlaire, Michel
    Comparative analysis of hedonic rents and maximum bids in a land-use simulation context2010In: Proceedings of the Swiss Transport Research Conference (STRC), Monte Verita/Ascona, Switzerland, 2010Conference paper (Refereed)
    Abstract [en]

    The choice and bid-auction approaches for location choice modeling are analyzed and compared, with a focus in their rent estimation models: hedonic prices and expected maximum bids, respectively. A simulation experiment is performed over synthetic data, comparing several specifications for hedonic rent models with the expected maximum bid. Results show that the hedonic approach generates rents that diverge from the maximum bids. This results indicate that hedonic rent models can be improved by accounting for elements like household’s heterogeneity in preferences and market conditions or constraints.

  • 82. Illenberger, J.
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Estimating network properties from snowball sampled data2012In: Social Networks, ISSN 0378-8733, E-ISSN 1879-2111, Vol. 34, no 4, p. 701-711Article in journal (Refereed)
    Abstract [en]

    This article addresses the estimation of topological network parameters from data obtained with a snowball sampling design. An approximate expression for the probability of a vertex to be included in the sample is derived. Based on this sampling distribution, estimators for the mean degree, the degree correlation, and the clustering coefficient are proposed. The performance of these estimators and their sensitivity with respect to the response rate are validated through Monte Carlo simulations on several test networks. Our approach has no complex computational requirements and is straightforward to apply to real-world survey data. In a snowball sample design, each respondent is typically enquired only once. Different from the widely used estimator for Respondent-Driven Sampling (RDS), which assumes sampling with replacement, the proposed approach relies on sampling without replacement and is thus also applicable for large sample fractions. From the simulation experiments, we conclude that the estimation quality decreases with increasing variance of the network degree distribution. Yet, if the degree distribution is not to broad, our approach results in good estimates for the mean degree and the clustering coefficient, which, moreover, are almost independent from the response rate. The estimates for the degree correlation are of moderated quality.

  • 83. Illenberger, Johannes
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Estimating properties from snowball sampled networks2011Report (Other academic)
  • 84. Illenberger, Johannes
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Kowald, Matthias
    Nagel, Kai
    A model for spatially embedded social networks2009In: Proceedings of the 12th International Conference on Travel Behaviour Research, Jaipur, India, 2009Conference paper (Refereed)
  • 85. Illenberger, Johannes
    et al.
    Flötteröd, Gunnar
    Ecole Polytech Fed Lausanne, Transport & Mobil Lab, CH-1015 Lausanne, Switzerland .
    Nagel, Kai
    A model of risk-sensitive route-choice behavior and the potential benefit of route guidance2011In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 12, no 2, p. 384-389Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a simulation-based investigation of the potential benefit of route-guidance information in the context of risk-sensitive travelers. We set up a simple two-route scenario where travelers are repeatedly faced with risky route-choice decisions. The risk averseness of the travelers is implicitly controlled through a generic utility function. We vary both the travelers' sensitivity toward risk and the equipment fraction with route-guidance devices and show that the benefits of guided travelers increase with their sensitivity toward risk.

  • 86. Illenberger, Johannes
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Nagel, Kai
    Enhancing MATSim with capabilities of within-day re-planning2007In: Proceedings of the 10th IEEE Intelligent Transportation Systems Conference, Seattle, USA, 2007Conference paper (Refereed)
  • 87. Illenberger, Johannes
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Nagel, Kai
    The role of spatial interaction in social networks2011Report (Other academic)
  • 88. Illenberger, Johannes
    et al.
    Nagel, Kai
    Flötterod, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    The Role of Spatial Interaction in Social Networks2013In: Networks and Spatial Economics, ISSN 1566-113X, E-ISSN 1572-9427, Vol. 13, no 3, p. 255-282Article in journal (Refereed)
    Abstract [en]

    This article addresses the role of spatial interaction in social networks. We analyse empirical data describing a network of leisure contacts and show that the probability to accept a person as a contact scales in distance with similar to d (-aEuro parts per thousand 1.4). Moreover, the analysis reveals that the number of contacts an individual possesses is independent from its spatial location and the spatial distribution of opportunities. This means that individuals living in areas with a low accessibility to other persons (rural areas) exhibit at average the same number of contacts compared to individuals living in areas with high accessibility (urban areas). Low accessibility is thus compensated with a higher background probability to accept other candidates as social contacts. In addition, we propose a model for large-scale social networks involving a spatial and social interaction between individuals. Simulation studies are conducted using a synthetic population based on census data as input. The results show that the model is capable of reproducing the spatial structure, but, however, fails to reproduce other topological characteristics. Both, the analysis of empirical data and the simulation results provide a further evidence that spatial interaction is a crucial aspect of social networks. Yet, it appears that spatial proximity does only explain the spatial structure of a network but has no significant impact on its topology.

  • 89. Kazagli, Evanthia
    et al.
    Bierlaire, Michel
    Flotterod, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Revisiting the route choice problem: A modeling framework based on mental representations2016In: Journal of Choice Modelling, ISSN 1755-5345, E-ISSN 1755-5345, Vol. 19, p. 1-23Article in journal (Refereed)
    Abstract [en]

    We present a new approach for modeling and analyzing route choice behavior. It is motivated by the need to reduce the complexity of the state-of-the-art choice models. It is inspired by the simplifications done by the travelers, using representations of their surrounding space. The proposed framework is based on elements designed to mimic the mental representations used by travelers, denoted as Mental Representation Items (MRIs). It allows the modeler to adjust the level of complexity according to the needs of the specific application. This paper describes how operational models based on MRIs can be derived and discusses the applications of these models to traffic assignment and route guidance systems. We report estimation results using revealed preference data to demonstrate the applicability and validity of the approach.

  • 90. Laemmel, Gregor
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    A CA model for bidirectional pedestrian streams2015In: 6TH INTERNATIONAL CONFERENCE ON AMBIENT SYSTEMS, NETWORKS AND TECHNOLOGIES (ANT-2015), THE 5TH INTERNATIONAL CONFERENCE ON SUSTAINABLE ENERGY INFORMATION TECHNOLOGY (SEIT-2015), Elsevier, 2015, p. 950-955Conference paper (Refereed)
    Abstract [en]

    The modeling of pedestrian flows is of particular importance for the planning of pedestrian facilities and the preparation for emergency situations. Even though there is a wide variety of simulation models on the market, a simulation model that deals with bidirectional pedestrian flow adequately is still missing. This contribution proposes an event-based cellular automaton model that is capable of simulating bi- and unidirectional pedestrian streams. The model is built on a theoretically sound foundation. Its performance is demonstrated by a comparison to empirical data.

  • 91. Lämmel, Gregor
    et al.
    Flötteröd, Gunnar
    Ecole Polytechnique Fédérale de Lausanne (EPFL).
    Towards system optimum: finding optimal routing strategies in time dependent networks for large-scale evacuation problems2009In: KI 2009: Advances In Artificial Intelligence, Proceedings / [ed] Mertsching, B; Hund, M, Springer Berlin/Heidelberg, 2009, p. 532-539Conference paper (Refereed)
    Abstract [en]

    Evacuation planning crucially depends on good routing strategies. This article compares two different routing strategies in a multi-agent simulation of: a large real-world evacuation scenario. The first approach approximates a Nash equilibrium, where every evacuee adopts an individually optimal routing strategy regardless of what this solution imposes on others. The second approach approximately minimizes the total travel time in the system, which requires to enforce cooperative behavior of the evacuees. Both approaches are analyzed in terms of the global evacuation dynamics and oil a detailed geographic level.

  • 92. Nagel, Kai
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Agent-based traffic assignment: going from trips to behavioral travelers2012In: Travel Behaviour Research in an Evolving World, Emerald Group Publishing , 2012Chapter in book (Refereed)
  • 93. Osorio, C.
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Zhang, C.
    A Metamodel Simulation-based Optimization Approach for the Efficient Calibration of Stochastic Traffic Simulators2015Conference paper (Refereed)
    Abstract [en]

    This work considers the calibration of stochastic microscopic traffic simulators. It formulates the calibration problem as a simulation-based optimization (SO) problem, and uses metamodel SO ideas. The main idea is to embed within the calibration algorithm an analytical problem-specific description of how the calibration parameters are related to the simulation-based objective function. Preliminary results on a toy network are presented. Ongoing work applies these ideas to the calibration of a Berlin metropolitan area network.

  • 94.
    Osorio, Carolina
    et al.
    MIT.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    A stochastic analytical kinematic wave model2012Report (Other academic)
  • 95. Osorio, Carolina
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Analytical approximation of joint queue-length distributions of a finite capacity queueing network2013Conference paper (Refereed)
  • 96. Osorio, Carolina
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Capturing Dependency Among Link Boundaries in a Stochastic Dynamic Network Loading Model2015In: Transportation Science, ISSN 0041-1655, E-ISSN 1526-5447, Vol. 49, no 2, p. 420-431Article in journal (Refereed)
    Abstract [en]

    This work adds realistic dependency structure to a previously developed analytical stochastic network loading model. The model is a stochastic formulation of the link-transmission model, which is an operational instance of Newell's simplified theory of kinematic waves. Stochasticity is captured in the source terms, the flows, and, consequently, in the cumulative flows. The previous approach captured dependency between the upstream and downstream boundary conditions within a link (i.e., the respective cumulative flows) only in terms of time-dependent expectations without capturing higher-order dependency. The model proposed in this paper adds an approximation of full distributional stochastic dependency to the link model. The model is validated versus stochastic microsimulation in both stationary and transient regimes. The experiments reveal that the proposed model provides a very accurate approximation of the stochastic dependency between the link's upstream and downstream boundary conditions. The model also yields detailed and accurate link state probability distributions.

  • 97.
    Osorio, Carolina
    et al.
    Massachusetts Institute of Technology.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Capturing dependency among link boundaries in a stochastic network loading model2012Conference paper (Refereed)
  • 98.
    Osorio, Carolina
    et al.
    mit.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Capturing dependency among link boundaries in a stochastic network loading model2012Conference paper (Refereed)
  • 99. Osorio, Carolina
    et al.
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Capturing queue dependency in an analytical stochastic network loading model2012In: Proceedings of the Annual Meeting of the Transportation Research Board, Washington DC, USA, 2012Conference paper (Refereed)
  • 100. Osorio, Carolina
    et al.
    Flötteröd, Gunnar
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Bierlaire, Michel
    A differentiable dynamic network loading model that yields full link state distributions and accounts for spillback2010In: Proceedings of the 3rd International Symposium on Dynamic Traffic Assignment, 2010Conference paper (Refereed)
123 51 - 100 of 106
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