Felix Schmid

Real-time Train Rescheduling in Junction Areas

On main line railways, sections with junctions are usually heavily used because of the converging flows of trains from different origins. In the event of disturbances, even a minor delay to one train can cause long consequential delays for following trains, because of conflicts in the junction areas and because, normally, less recovery time and margin time are allocated where trains travel through bottleneck sections. Depending on the performance regime, train rescheduling can be an effective method to decrease the overall delay and any penalty payment. The authors of this article propose a decision support methodology for real-time train rescheduling in junction areas, based on a mathematical approach that optimizes an objective function. Their Junction Rescheduling Model (JRM) solves certain types of junction rescheduling problems by using an improved differential evolution algorithm for JRM that achieves near optimal solutions. They also present a statistical evaluation of the algorithm performance compared with the first-come-first-served strategy, based on the Monte-Carlo simulation methodology.

Overcoming barriers to transferring systems engineering practices into the rail sector

There is increasing interest within the rail sector in applying the concepts of systems engineering. This paper presents arguments that the balance of concerns differs between a typical project in the rail sector and one in the domains in which systems engineering was developed and that this difference, together with a lack of agreement on the scope of systems engineering and differences in tradition between systems engineering and the established rail disciplines, raise barriers to the effective and efficient importation of systems engineering ideas into the rail sector. It is suggested that the system engineering community can lower these barriers by strengthening published systems engineering guidance in certain areas, being prepared to express themselves in plain language and packaging their practices in a more portable fashion, while the rail community can help by being prepared to adapt the systems engineering approach to meet their needs better and introducing new practices in a measured and systematic fashion. The benefits to both communities are identified and found to justify the investment required to take these steps.

Benchmarking and evaluation of railway operations performance

Abstract A prototype evaluation framework has been used in railway traffic simulator benchmarking and in the quantitative evaluation and comparison of timetables and of real time traffic management decision taking for railway systems in the presence of both small and large-scale service disruption in the EU FP7 project ON-TIME. Quantified key measures allow an assessment of performance and can be used to compare timetables, control methods or delaying incidents. The resilience measures additionally provide a visualisation and information that can be analysed as an aid to the understanding of delay propagation, based on both real and simulated data. This benchmarking and evaluation method is based on collecting data at selected observation points on train and service ID, position, and time from either simulation or from data feeds of real operations. With the addition of data on train and network characteristics, this collected data can be processed in such a way as to evaluate the key measures outlined in a previously defined Quality of Service framework. The key measures quantify the following KPIs of the model: transport volume, journey time, connectivity, punctuality, resilience, energy consumption and resource usage.

Managing incidents in a complex system: a railway case study

The authors of this paper review how complex entities, composed of many interdependent subsystems, such as international rail operators, can improve their ability to recover from incidents through the better management of key interfaces. The principles of Normal Accident Theory and resilience engineering are discussed, and the case study of the Eurostar incident of 18–19 December 2009 is considered in detail. Lessons learnt from resilience engineering are applied to the case study to extract recommendations by which incident management for open access international rail transport may be improved.

Rail vehicle impact analysis: A critique of the suitability of the rigid wall model and the assumption of symmetrical behaviour

This paper studies the accuracy of rigid-wall (stonewall) and symmetric models in rail vehicle impact stability. The investigation is based on modelling results and theoretical analysis. The theoretical investigation consists of a mechanical description of the conservation of energy transformation and instability of train impact due to irregular structural collapse and loose coupling patterns. It is shown that an unstable response is a common consequence in vehicle impacts and the corresponding stiffness amongst cross-sections has a strong effect on collapse stability. The modelling investigation summarises impact simulations of a cab vehicle. This illustrates the pitfalls of the rigid-wall and symmetric models as follows: firstly, using a rigid wall in modelling could mask irregular deformations and lead to overestimated crashworthy performance behaviours; and secondly, symmetric impacts could lead to asymmetric deformations resulting in crucial irregular responses of rail vehicles being missed. This paper explores the irregular responses of rail vehicles in train collisions and highlights the relevant issues which might be overlooked when conventional static approaches are used in dynamic scenarios. It is anticipated that the paper will provide increased insight into impact mechanics of rail vehicles and promote a rethink about the influence of characteristic behaviours in dynamic responses resulting in a more accurate representation.

A novel framework for supporting the design of moving block train control system schemes

A moving block philosophy is increasingly being implemented as part of communications-based train control (CBTC) systems in mass transit operations. Due to its complexity and safety criticality, it is difficult to develop formal methods to support the design of specific schemes. An innovative framework, based on topology mathematics, for supporting CBTC moving block system development is proposed in this paper. Within the new framework, the moving block train control logic is transformed into topological spaces representing the movement authority for trains. Using this approach, the verification of logic and safety properties can be performed by automatic assessment of the topological space. Within the paper the essential characteristics of moving block systems, train behaviour and static track-side infrastructure are analysed. As a result of this analysis, topological units are formed to represent train movement trajectory and standard railway network elements. Four calculation methods: dividing, trimming, covering and integrating, are described as standard unit operations. Finally, a case study is implemented to demonstrate how the method is advantageous for CBTC scheme layout development. It is found that the approach is able to bridge the gap between traditional, highly abstracted, formal methods and the specific safety-critical railway scheme designs.

Modeling and Solving Real-Time Train Rescheduling Problems in Railway Bottleneck Sections

There usually exists a high density of traffic through bottleneck sections of mainline railways, where a perturbation of one single train could result in long consequential delays across a number of trains. In the event of disturbances, rescheduling trains approaching the bottleneck will be necessary to increase the throughput of the section. To model the real-time train rescheduling problems around bottleneck sections, a mixed-integer programming model is presented in this paper. An innovative improved algorithm (DE_JRM) is developed to solve the problem. The model and the algorithms are validated with a case study using Monte Carlo methodology, which demonstrates that the proposed algorithm can reduce the weighted average delay and satisfy the requirements of real-time traffic control applications.

Rail vehicle impact analysis: The instable propensity of structural responses and the critical scenarios of structural failure

In this paper, the authors investigate the characterisation of the structural collapse of steel-bodied rail vehicles and propose modifications to a cab structure for improved structural crashworthiness. This is a mechanical- and simulation-based investigation, comprising three parts: after a mechanical description of the impact forces and energy conservation in collisions between trains, the characteristics of rail vehicle structures are examined to identify structural weaknesses in the context of impact stability. This is followed by a computer simulation of a cab structure to validate the conclusions from the theoretical analysis and to demonstrate the effectiveness of the design modifications. Focusing on the correlation between structural characterisation and impact stability, the authors highlight the following three findings: first, rail vehicles have a propensity to be unstable in the vertical direction due to the asymmetrical geometry and unbalanced impact loads; second, high shear stresses tend to be generated at the top corners of the rear pillars of the door region, leading to a localised fracture tendency; and third, impact stability can be enhanced through structural modifications by adopting symmetric cross sections or enhancing the stiffness in the weak direction for asymmetric structures, i.e. achieving geometric symmetry or stiffness balance on impact. The findings result in a better understanding of the mechanisms in structural crushing and advance the research into passive safety of rail vehicles.

Feasibility of discontinuous electrification on the Great Western Main Line determined by train simulation

The UK has a number of main line railway routes that are not yet electrified. Some of these routes are under active consideration for electrification and the UK Government has recently announced the electrification of the Great Western Main Line (GWML). Railway electrification requires a large capital investment in infrastructure. Areas with limited clearance, such as tunnels and sections through overbridges, are particularly expensive to electrify. In this paper, train performance on the GWML, from London Paddington to Cardiff and vice versa, is modelled for three cases: no electrification; full electrification; and electrification that does not include tunnels, most notably the Severn Tunnel. The modelled trains were: the High Speed Train hauled by pairs of Class 43 diesel-electric locomotives; the nine-car Class 390; and Intercity Express Programme (IEP) trains formed as straight electric or bi-mode multiple units. Bi-mode trains combine electric and diesel traction in the same train. The considered IEP trains included both five-car and eight-car bi-mode options. Journey time, energy consumption and CO2 emissions were determined in each case. Electrification of the route will result in a reduction in energy consumption, carbon emissions and journey time, with the longest trains offering the greatest benefit. Under normal conditions, all modelled trains were able to complete the journey under discontinuous electrification. However, a small reduction in entry speed into the Severn Tunnel resulted in stalling of the exclusively electric trains. Bi-mode rail vehicles completed the journey in all cases and, as to be expected, also when tunnel entry speed is reduced; journey time, energy consumption and carbon emissions are not majorly impacted compared to exclusively electric operation.

Evaluation of Permanent Magnet Motor energy saving technology for different types of railways

The majority of drive chain losses in railway vehicles are attributable to motor inefficiency. An attractive solution to reduce these losses, and the associated energy consumption, is the implementation of Permanent Magnet Synchronous Motor (PMSM) technology. PMSMs are not only more efficient, but smaller and lighter than traditional induction machines, which can further benefit energy saving. However, introducing this technology and the associated control systems can be expensive and complex. Therefore, in this study, the authors evaluate the cost benefit of introducing PMSMs into different railway sub-modes to see where this solution is most appropriate, in terms of energy saved. The impact of regenerative braking on the cost is also considered, by simulating dynamic braking characteristics and the receptivity of different systems.