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See detailDynamic Origin-Destination Matrix Estimation on Large-Scale Congested Networks Using A Hierarchical Decomposition Scheme
Frederix, Rodric; Viti, Francesco UL; Tampere, Chris M.J.

in Journal of Intelligent Transportation Systems (2014), 18(1), 51-66

Despite the ever increasing computing power, dynamic Origin-Destination (OD) estimation in congested networks remains troublesome. In previous research, we have shown that an unbiased estimation requires ... [more ▼]

Despite the ever increasing computing power, dynamic Origin-Destination (OD) estimation in congested networks remains troublesome. In previous research, we have shown that an unbiased estimation requires the calculation of the sensitivity of the link flows to all Origin Destination flows, in order to incorporate the effects of congestion spillback. This is however computationally infeasible for large-scale networks. To overcome this issue, we propose a hierarchical approach for off-line application that decomposes the dynamic OD estimation procedure in space. The main idea is to perform a more accurate dynamic OD estimation only on subareas where there is congestion spillback. The output of this estimation is then used as input for the OD estimation on the whole network. This hierarchical approach solves many practical and theoretical limitations of traditional OD estimation methods. The main advantage is that different OD estimation method can be used for different parts of the network as necessary. This allows applying more advanced and accurate, but more time consuming methods only where necessary. The hierarchical approach is tested on a study network and on a real network. In both cases the proposed methodology performs better than traditional OD estimation approaches, indicating its merit. [less ▲]

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See detailModels and Technologies for Intelligent Transportation Systems: new challenges and metaheuristic solutions for large-scale network applications
Viti, Francesco UL; Tampere, Chris M.J.

in Journal of Intelligent Transportation Systems (2014), 18(1), 1-4

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See detailEvaluation of intervention strategies for a road link in the Netherlands
Adey, Bryan Tyrone; Lethanh, Nam; Hartmann, Andreas et al

in Built Environment Project and Asset Management (2014), 4(2), 180-198

Purpose – The purpose of this paper is to investigate the use of the impact hierarchy and the optimization model to determine the optimal intervention strategy for a road link composed of multiple objects ... [more ▼]

Purpose – The purpose of this paper is to investigate the use of the impact hierarchy and the optimization model to determine the optimal intervention strategy for a road link composed of multiple objects. The paper focusses on the results of a case study of intervention project on A20 road link in Rotterdam, the Netherlands. Design/methodology/approach – The study was a case study research. It describes briefly the impact hierarchy and its link to the optimization model, and then focussed on analyzing the results obtained from running the model. In order to understand the influence of various factors affecting the results of optimization, sensitivity analysis was performed. Findings – The proposed hierarchy is suitable to be used to support the determination of optimal intervention strategies (OISs) for public road. From the case study, it was also realized that optimal intervention strategy can be changed due to not only intervention costs incurred by the owner, but also due to the setup of traffic configuration during the execution of interventions since the impacts incurred to users, directly affected public, and indirectly affected public are significantly different from one traffic configuration to the others. The optimal intervention strategy also depends greatly on the factors of deterioration during the operation of the infrastructure objects. Research limitations/implications – In the impact hierarchy, some impact factors are difficult to be quantified, e.g., the long-term economic impacts on the region where having intervention projects. The use of only exponential function for impacts could be oversimplified the actual behavior of the impacts. Other functional form should be investigated to be used within the framework of the optimization model. Practical implications – The proposed hierarchy and the optimization model could be used in practical situation for determination of OISs for multiple objects within a road link. Originality/value – This paper contributes to the body of knowledge of stakeholder analysis in the field of infrastructure asset management. It also gives a guideline and tool for infrastructure administrators to select the OISs for their infrastructure network. [less ▲]

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See detailCalibration of a microscopic simulation model for emission calculation
Li, Jie; Van Zuylen, Henk J.; Chen, Yusen et al

in Transportation Research. Part C : Emerging Technologies (2013), 31

Emissions by road traffic can be reduced by optimising traffic control. The impact of this optimisation on emission can be analysed ex ante by simulation. The simulation programs used for this analysis ... [more ▼]

Emissions by road traffic can be reduced by optimising traffic control. The impact of this optimisation on emission can be analysed ex ante by simulation. The simulation programs used for this analysis should be valid with respect to the traffic characteristics that determine the emissions. Thus calibration of the parameters is a prerequisite. In most cases, volumes, travel times and queues are used to calibrate simulation models, rather than detailed driving characteristics such as speed and acceleration patterns. However, these driving behaviour parameters determine the vehicular emissions to a great extent. A study was carried out in which the driving behaviour parameters in a microscopic simulation model (VISSIM) were calibrated using real trajectories collected by image processing at an intersection in Rotterdam. The sensitivity of the simulation results for driving behaviour parameters was investigated. The most influential parameters were identified and adjusted to ensure that the simulation results were consistent with the observed traffic and could provide valid estimations of the total production of emissions. [less ▲]

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See detailA Null-Space metric for the analysis of partial network observability in sensor location problems
Rinaldi, Marco; Viti, Francesco UL; Corman, Francesco

Scientific Conference (2013)

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See detailDynamic OD estimation in congested networks: theoretical findings and implications in practice
Frederix, Rodric; Viti, Francesco UL; Tampere, Chris M.J.

in Transportmetrica (2013), 9(6), 494-513

In this study we analyse the impact of congestion in dynamic origin–destination (OD) estimation. This problem is typically expressed using a bi-level formulation. When solving this problem the ... [more ▼]

In this study we analyse the impact of congestion in dynamic origin–destination (OD) estimation. This problem is typically expressed using a bi-level formulation. When solving this problem the relationship between OD flows and link flows is linearised. In this article the effect of using two types of linear relationship on the estimation process is analysed. It is shown that one type of linearisation implicitly assumes separability of the link flows, which can lead to biased results when dealing with congested networks. Advantages and disadvantages of adopting non-separable relationships are discussed. Another important source of error attributable to congestion dynamics is the presence of local minima in the objective function. It is illustrated that these local minima are the result of an incorrect interpretation of the information from the detectors. The theoretical findings are cast into a new methodology, which is successfully tested in a proof of concept. [less ▲]

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See detailAn Iterative Learning Approach for Signal Control in Urban Traffic Networks
Huang, Wei; Viti, Francesco UL; Tampere, Chris M.J.

in Proceedings of IEEE-ITS Conference (2013)

Traffic signal control influences route choice in traffic networks, and may even determine whether a traffic system settles in equilibrium or destabilizes into oscillatory patterns. Ideally, a stable ... [more ▼]

Traffic signal control influences route choice in traffic networks, and may even determine whether a traffic system settles in equilibrium or destabilizes into oscillatory patterns. Ideally, a stable equilibrium flow pattern should result from the interaction between control and route choice on a long-term horizon. This paper proposes an iterative learning approach for designing signal controls able to attract the system to equilibrium in an acceptable convergence speed. The traffic assignment model and combined traffic assignment and control problem are first introduced. An iterative learning control (ILC) based signal control is formulated and a basic model inversion method is analyzed. To deal with the nonlinearity of traffic system, a Newton based ILC algorithm is applied. Test in an example network verifies the effectiveness of the ILC method in achieving stable equilibrium in the traffic system. [less ▲]

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See detailEquilibrium in capacitated network models with queueing delays, queue-storage, blocking back and control
Smith, Mike J.; Huang, Wei; Viti, Francesco UL

in Procedia Social and Behavioral Sciences (2013), 80

This paper considers a steady-state, link-based, fixed (or inelastic) demand equilibrium model with explicit link-exit capacities, explicit bottleneck or queuing delays and explicit bounds on queue ... [more ▼]

This paper considers a steady-state, link-based, fixed (or inelastic) demand equilibrium model with explicit link-exit capacities, explicit bottleneck or queuing delays and explicit bounds on queue storage capacities. The (spatial queueing) model at the heart of this equilibrium model takes account of the space taken up by queues both when there is no blocking back and also when there is blocking back. The paper shows in theorem 1 that a feasible traffic assignment model has an equilibrium solution provided prices are used to impose capacity restrictions and utilises this result to show that there is an equilibrium with the spatial queueing model, provided queue-storage capacities are sufficiently large. Other results are obtained by changing the variables and sets in theorem 1 suitably. These results include: (1) existence of equilibrium results (in both a steady state and a dynamic context) which allow signal green-times to respond to prices and (2) an existence of equilibrium result which allow signal green-times to respond to spatial queues; provided this response follows the P0 control policy in Smith (1979, 1987). These results show that under certain conditions the P0 control policy maximises network capacity. The spatial queueing model is illustrated on a simple network. Finally the paper includes elastic demand; this is necessary for long-run evaluations. Each of the steady state models here may be thought of as a stationary solution to the dynamic assignment problem either with or without blocking back. [less ▲]

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See detailSignal control strategies in day-to-day dynamic process of combined traffic assignment and control
Huang, Wei; Viti, Francesco UL; Tampere, Chris M.J.

Scientific Conference (2013)

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See detailDynamic modeling of VISSIM critical gap parameter at unsignalized intersections
Viti, Francesco UL; Wolput, Bart; Tampere, Chris M.J. et al

Poster (2013)

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See detailProceedings of the BIVEC-GIBET Transport Research Days 2013
Hesse, Markus UL; Caruso, Geoffrey UL; Gerber, Philippe et al

Book published by University Press (2013)

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See detailTravel-sharing in multimodal systems: a behavioural modelling approach
Viti, Francesco UL

Scientific Conference (2013)

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See detailEvaluating the effects of information reliability on travellers’ route choice
Bifulco, Gennaro N.; Di Pace, Roberta; Viti, Francesco UL

in European Transport Research Review (2013)

Purpose This paper analyses travellers’ behaviour with respect to route choice in a context where an Advanced Traveller Information System (ATIS) is in place. ATIS are important applications in the field ... [more ▼]

Purpose This paper analyses travellers’ behaviour with respect to route choice in a context where an Advanced Traveller Information System (ATIS) is in place. ATIS are important applications in the field of intelligent transportation systems (ITS). However, the practical impact of ATIS is still a matter for debate, and identification of expected route choice behaviour under ATIS is one of themain ways to assess their practical importance. Methods Travellers’ choices are frequently explored by means of stated preference (SP) approaches. In this paper we discuss some issues to be addressed when an SP survey is carried out, with particular reference to cases where a repeated choice approach is employed in the survey. Results Our analysis concerns an application of the SP approach in a pilot study aimed at identifying the effects of ATIS accuracy on travellers’ compliance with information. Conclusions This paper aims tomake two major contributions. First of all, empirical analyses based on proper indicators and statistical tests are suggested in order to evaluate how the collected data have to be handled in order to eliminate transient route-choice observations. These are due to the warm-up phase inherently associated with the survey method adopted, dealing with repeated choices. Secondly, we analyse (stationary) route choice in order to assess the effects of information reliability (and the kind of information) on both route choice and compliance. [less ▲]

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See detailCombining demand management and merge control in an equilibrium network model
Viti, Francesco UL; Huang, Wei; Smith, Mike J.

Scientific Conference (2013)

Equilibrium models under congested traffic conditions, and especially those addressing blocking back, are very useful to estimate the demand conditions that ITS policies should be able to manage, for ... [more ▼]

Equilibrium models under congested traffic conditions, and especially those addressing blocking back, are very useful to estimate the demand conditions that ITS policies should be able to manage, for instance to maintain congestion within controlled areas and avoiding that they further spillback and cause more serious and/or less controllable congestion states. The objective of this paper is to supplement the equilibrium model, developed by the authors in recent research, with a more thorough analysis of merge behaviour, especially in cases of blocked nodes. Regulating the merger behaviour together with the demand pattern can lead to certain desired stationary states. It has a great practical significance when congestion is inevitable, while demand management and merge control are able to retain queues and spill-backs within the local area. [less ▲]

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See detailEquilibrium and sensitivity analysis of dynamic ridesharing
Viti, Francesco UL; Corman, Francesco

Scientific Conference (2013)

Sharing travels is an effective way to increase car occupancy rates and to reduce the number of cars for the same distances traveled. This is a problem involving operations research (how to best match ... [more ▼]

Sharing travels is an effective way to increase car occupancy rates and to reduce the number of cars for the same distances traveled. This is a problem involving operations research (how to best match travels in time and space, what level of similarity for the routes,…) and behavior challenges (on which conditions users choose to share travels, which type of users is willing to share the travel, what is the accepted detour and rescheduling, …). This research aims at filling the gap in the latter aspect by proposing an equilibrium modeling approach for (dynamic) ridesharing. By using a Nested logit model, , greater insight into the impact of different policies, behavioral factors and matching criteria can be presented. We deal with a theoretically interesting basic model structure of a single-link case, in which we study the complex interaction of multiple factors, and the joint sensitivity to the most relevant parameters. This allows us to derive some basic recommendations from the equilibrium states reached. [less ▲]

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See detailQuantifying partial observability in network sensor location problems
Viti, Francesco UL; Rinaldi, Marco; Corman, Francesco

Scientific Conference (2013)

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