1,720,983 research outputs found
Enhancing timetable planning with stochastic dwell time modelling
No full textEstimating stop time is a critical task for timetable planning, especially since actual dwell time shows a significant variability that could hinder service reliability. Therefore its importance has increased as railways seek to maximize infrastructure utilization while improving the quality standards, including reliability.
A significant amount of scientific work focussing on the estimation of dwell time within different transit systems can be found in literature. However, it is mostly focused on aspects such as, for example, the time required for each passenger to board depending on the number of steps, while in very few reports the applicability of the models and their practical relevance are described.
This study presents an approach for estimating the stop time distribution of train services and using them in simulation or timetable planning tools. Based on conventional parameters on the one hand and on track occupancy data collected by train describers on the other, the models include an algorithm to derive the stop time from the track occupancy data and a multi-parametric dwell time estimation.
When past track occupancy data is available, the parameters are estimated: the calibrated model can be used as input to plan or simulate future scenarios considering, for example, new rolling stock or different service patterns.
The results of model calibration and its use in a test network around Venice are described in the last part of the paper
An approach for Calibrating and Validating the Simulation of complex rail networks 
No full textThis paper presents an approach for the estimation of the stochastic inputs for the simulation of railway operations on the basis of real data. The use of stochastic process-times appears particularly relevant on complex networks, where the interactions among trains and their behaviour can vary significantly compared to the planned timetable.
The method was developed to allow the quick preparation and validation of the simulation models for the most important parts of the Italian network . It has already been tested on networks with up to 1000 trains/day before becoming widespread for assessing the impact of infrastructure and timetable improvements as well as for estimating ex-ante the reliability of timetables. The primary advantage of the approach is the very low effort required to define the data sets on the basis of data collected automatically, as well as the simple generation of realistic simulation scenarios. These characteristics were the key factors for the use of the approach in large scale
Capacity vs Reliability in railways: A stochastic micro-simulation approach
No full textRailway transport is increasing its strategic role at urban, national and international level both for passenger and freight mobility. In fact, road traffic congestion causes decreasing levels of service and railways can become more and more reliable thanks to recent investments in infrastructures and technology. In recent years, the unexpected economic crisis is forcing planners to find less expensive and easier to build measures, which effectiveness has to be demonstrated before being approved.
As a result, quantitative methods have to be used, which allow a precise capacity estimati- on, also considering different timetable scenarios, interlocking systems and infrastructure layouts. Moreover, since a high traffic reliability level has to be offered, the effects of incre- asing traffic on punctuality have to be taken into consideration while estimating capacity.
In this paper a methodology is presented, one which allows a precise estimation of the tra- de–off between capacity and reliability on railway networks and identifies the system bottle- necks. This methodology is based on stochastic micro–simulation of rail traffic, which has been calibrated using extensive real life data. The successful results obtained using the met- hodology in important sections of two Pan–European corridors are described and discussed in the second part of the paper. The first case study deals with the network between Trieste and Venice, on the Corridors N.5 and 23; it plays a crucial role at a continental level, since it represents the connection between Italy and all countries of Central and Eastern Europe. The second application focuses on the Croatian part of the 9 Corridor (Dobova–Zagreb–Tovarnik), which connects Germany and Austria with the Balkan Area
Un approccio per la determinazione dell'equilibrio tra capacità e regolarità dei servizi ferroviari
No full textLa qualità dell'esercizio è un parametro fondamentale per la competitività del trasporto ferroviario passeggeri. La crescente saturazione dei nodi e delle linee e la contemporanea necessità di aumentare la regolarità del servizio offerto impongono ai gestori un deciso aumento nella precisione della pianificazione dell'esercizio anche mediante una modellizzazione più accurata delle diverse variabili stocastiche e deterministiche che lo influenzano.
In questo contesto, il presente lavoro propone inizialmente una valutazione dei diversi tempi tecnici e dei fenomeni stocastici che possono influire sulla qualità dell'esercizio. In particolare sono stati analizzati i tempi di occupazione e gli intertempi minimi in presenza dei diversi sistemi di distanziamento e sicurezza, quindi le variabilità in partenza, nei tempi di percorrenza e di sosta. Successivamente vengono discussi alcuni provvedimenti da adottare in fase di pianificazione dell’esercizio per limitare le ricadute sulla regolarità di fenomeni e perturbazioni stocastiche.
Le diverse variabili sono state analizzate con particolare riferimento al nodo di Lucerna (CH), che è scelto in virtù della topologia relativamente semplice e dell'elevata densità di traffico presente, mentre l’analisi degli effetti di diversi provvedimenti è stata condotta attraverso un modello calibrato di microsimulazione sincrona e stocastica della circolazione ferroviaria
Structure and Simulation Evaluation of an Integrated Real-Time Rescheduling System for Railway Networks
No full textA critical problem faced by railways is how to increase capacity without investing heavily in infrastructure and impacting on schedule reliability. One way of increasing capacity is to reduce the buffer time added to timetables. Buffer time is used to reduce the impact of train delays on overall network reliability. While reducing buffer times can increase capacity, it also means that small delays to a single train can propagate quickly through the system causing knock-on delays to trains impacted by the delayed train. The Swiss Federal Railways (SBB) and Swiss Federal Institute of Technology (ETH) are researching a new approach for real-time train rescheduling that could enable buffer times to be reduced without impacting schedule reliability. This approach is based on the idea that if trains can be efficiently rescheduled to address delays, then less buffer time is needed to maintain the same level of system schedule reliability. The proposed approach combines a rescheduling algorithm with very accurate train operations (using a driver-machine interface). This paper describes the proposed approach, some system characteristics that improve its efficiency, and results of a microscopic simulation completed to help show the effectiveness of this new approach. The results demonstrate that the proposed integrated real-time rescheduling system enables capacity to be increased and may reduce knock-on delays. The results also clearly showed the importance of accurate train operations on the rescheduling system's effectiveness
Multi-criteria Analysis to Support Mobility Management at a University Campus
Get PDFThe mobility referred to the University is a significant part of the urban mobility in Trieste. Therefore a specific project was performed to analyze the main problems, to understand the preference structure of the users and to define some possible solutions to improve the accessibility of the University and to reduce urban congestion, mainly through sustainable transport modes. The survey pointed out features and preferences of different user groups, which were explicitly considered in the AHP assessment framework, and allowed to define criteria and to fix the weights. Also the presence of more than one decision maker was explicitly included in the hierarchy, to model the different impact of different user groups on the decision makers. As a result, the ranking of the alternatives has been defined, which has been taken into account by the decision makers for their planning choices. From a methodological point of view, the specific structure of the AHP hierarchy allowed to model the decisional problem even if a more complex ANP approach would be perhaps more suitable to consider interactions between nodes in this group decision problem
Using simulation to assess infrastructure performance in multicriteria evaluation of railway projects
No full textEconomic evaluation of projects of new railway infrastructures is a typical step of feasibility studies, but it is rather common to take into account other than transport aspects of projects
such as their environmental or land use outcomes. Multicriteria methodologies may support decision makers during the process of evaluation and choice of candidate projects; notwithstanding a large part of the applications in the railway sector carry out a careful analysis of the negative impacts of the alternatives, but the reasons for the actual realization of the project are neglected. In fact, a railway infrastructure project aims to improve an existing situation by means of expected positive effects on, for example, accessibility or travel times. Nonetheless, the economic revenues, the positive effects on the social sphere or the specific transportation–related matters that a project might generate are often left in the background. The authors propose a model that includes different attributes that can characterize a railway infrastructure, e.g. the flexibility rate, the comfort offered to travellers, the access times to stations, the vehicle maintenance savings, the served population, the
ticketing revenues. Thus the aim of this paper is to introduce a new structure for the decision problem that includes criteria related to the positive outcomes of each alternative project as
well as its negative effects. It is worth noting that positive outcomes are, to a great extent, measurable directly or they can be assessed by means of simulation models. Some of the
transport–related criteria are indeed related to the inputs and outputs of stochastic simulation, which can reproduce most processes involved in rail traffic, including deterministic
aspects and human factors. This is particularly relevant in order to simulate traffic under realistic conditions, considering variability at border, various driving styles and stop times
Automated analysis of train event recorder data to improve railway simulation
No full textIn recent years on board digital train event recorder have been developed: these devices allow to collect very detailed data about train movements and signal status. The new Italian ATC SCMT on board subsystem is combined with the DIS (Driver Information System) that collects both kinetic behaviour and all signal and balises messages. Unfortunately, this large amount of data is normally stored but not used except for failure and maintenance management.
At the same time the use of micro simulation tools has been extended to large scale problems. As known a problem exists in the calibration and validation of these models.
In this paper a new tool is presented. This tool allows to analyse real-life collected data, to perform very detailed analysis of train movements, pointing out speed depending on position and signal aspects, acceleration, braking curves and dwell time graphically and by means of parameters. Train behaviour can also be connected to punctuality, to find out differences between on time and late running.
This tool may be very useful for: large scale model validation, definition of the stochastic behaviour of the system (travel time, dwell time, initial delay), calibration of braking and acceleration curves for various train types, acceleration percentage depending on different conditions. In other words, it allows to set up a link between real data and micro simulation models.
The tool has been tested in the north-eastern part of Italy. In this case study, a significant precision increase in the stochastic simulation results has been reached
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