Analysis of Platooning Train Operations under V2V communication-based signalling:: fundamental modelling and capacity impacts of Virtual Coupling

The ever-increasing need for railway capacity has led infrastructure managers to explore next generation signaling systems to drastically reduce train separation by overcoming traditional fixed-block railway operations. Technologies like ETCS Level 3 are under development to bring the railways to a configuration without track-side signaling where trains move at an absolute braking distance from each other. The railway industry is however looking into the alternative concept of Virtual Coupling which separates trains by a relative braking distance as for cars on the road. By means of a V2V communication architecture trains could move synchronously in platoons which could be treated as a single convoy at junctions, so to improve capacity. On the other hand, the concept might introduce additional safety risks, especially at diverging junctions where points need to be switched and locked in between trains of a platoon. There is the need to understand whether capacity benefits provided by Virtual Coupling are sufficient to motivate the railway industry to invest in it, despite the unclear safety implications. This paper addresses such a need by assessing impacts of Virtual Coupling on railway capacity and potential benefits with respect to ETCS Level 3. For the first time in literature, operational principles and capacity occupation models have been developed and simulated to describe train operations under Virtual Coupling. An application to a case study in the UK shows the advantages that such a concept provides in terms of capacity utilization, as well as space and time train headways.Accepted Author ManuscriptTransport and Plannin

A comparative analysis of Virtual Coupling Railway operations

Virtual Coupling is a next-generation signalling concept conceived to increase railway capacity by bringing moving-block operations one step further to separating trains by a relative braking distance, like cars on the road. Thanks to a Vehicle-to-Vehicle (V2V) communication layer, trains can move in virtually coupled platoons which can be treated as single convoys at junctions to improve capacity. This concept however introduces the need for additional operational constraints, especially at diverging junctions, which could make capacity gains insufficient to justify investments. The railway industry is hence investigating the benefits that Virtual Coupling can offer with respect to moving-block and fixed-block signalling systems. This paper introduces operational principles and an innovative train-following model capturing operational states and corresponding transitions of Virtual Coupling train operations. A comparative capacity analysis is conducted for a portion of the South West Main Line in the UK. Promising results are obtained, showing that the biggest capacity gains of Virtual Coupling refer to operational scenarios normally found in practice with trains having service stops and using different routes. The analysis of multiple disturbed scenarios reveals that performance improvements of Virtual Coupling over moving-block are instead only marginal on low-speed networks.Accepted Author ManuscriptTransport and Plannin

Exploring Virtual Coupling: operational principles and analysis

Virtual Coupling is a next-generation signalling concept conceived to increase railway capacity by bringing moving-block operations one step further to separating trains by a relative braking distance, like cars on the road. Thanks to a Vehicle-to-Vehicle (V2V) communication layer, trains can move in virtually coupled platoons which can be treated as single convoys at junctions to improve capacity. This concept however introduces the need for additional operational constraints, especially at diverging junctions, which could make capacity gains insufficient to justify investments. The railway industry is hence investigating the benefits that Virtual Coupling can offer with respect to moving-block and fixed-block signalling systems. This paper introduces operational principles and an innovative train-following model capturing operational states and corresponding transitions of Virtual Coupling train operations. A comparative capacity analysis is conducted for a portion of the South West Main Line in the UK. Promising results are obtained, showing that the biggest capacity gains of Virtual Coupling refer to operational scenarios normally found in practice with trains having service stops and using different routes. The analysis of multiple disturbed scenarios reveals that performance improvements of Virtual Coupling over moving-block are instead only marginal on low-speed networks.Accepted Auhtor ManuscriptTransport and Plannin

Assessing Hyperloop Transport Capacity Under Moving-Block and Virtual Coupling Operations

The Hyperloop is a concept of a ground transportation system consisting of capsules traveling at very high-speeds in near-vacuum tubes. The Hyperloop aims to be a fast, cheap, and sustainable alternative to short-haul flights and high-speed rail. The small pod size requires very high frequencies to respond to future high levels of passenger and cargo demands. Media and representatives of the emerging Hyperloop industry acclaim the Hyperloop as a very capacity effective transport system, however there is no clear scientific evidence proving that. A theoretical investigation is therefore necessary to understand which capacity the Hyperloop could safely provide. This paper provides a comparative analysis of the capacity that the Hyperloop can offer for several operational scenarios and different signalling systems, including Moving-Block and the advanced concept of Virtual Coupling. Results show that Moving-Block could achieve required transport capacity levels only if pods could use high deceleration rates likely to be unsafe and uncomfortable to passengers. Virtual Coupling is instead observed to be a more satisfactory operational concept that could provide a higher transport capacity while respecting safety and comfort standards if reliable pod platooning technologies are available.Accepted Author ManuscriptTransport and Plannin

Assessing Hyperloop Transport Capacity under Moving-Block and Virtual Coupling Operations

The Hyperloop is a concept of a ground transportation system consisting of capsules (called pods) traveling at very high-speeds in near-vacuum tubes. The hyperloop aims to be a fast, cheap, and sustainable alternative to short-haul flights and high-speed rail. The small pod size requires very high frequencies to respond to future high levels of passenger and cargo demands. Media and representatives of the emerging Hyperloop industry acclaim the Hyperloop as a very capacity-effective transport system, however there is no clear scientific evidence proving that. A theoretical investigation is therefore necessary to understand which capacity the Hyperloop could safely provide and whether that could satisfy the future transport demand. This paper provides a comparative analysis of the capacity that the Hyperloop can offer for several operational scenarios and different signalling systems, including Moving-Block and the advanced concept of Virtual Coupling. Results show that Moving-Block could achieve required transport capacity levels only if pods could use high deceleration rates likely to be unsafe and uncomfortable to passengers. Virtual Coupling is instead observed to be a more satisfactory operational concept that could address transport demand while respecting safety and comfort standards if reliable pod platooning technologies are available.Accepted Author ManuscriptTransport and Plannin

Resolving instability in railway timetabling problems

A growth of the railway transportation demand is forecasted in the next decades which needs an increase of network capacity. Where possible, infrastructure upgrading can release extra capacity, although in some cases this is not enough to satisfy the entire transportation demand unless optimised timetabling is performed. We propose a heuristic approach to develop a stable and timetable which maximise the satisfaction of transportation demand in situations where network capacity is limited. In case the demand cannot be fully satisfied, the model relaxes the given line plan and timetable design parameters. In addition, the aim is to maximize the satisfied demand by keeping as many train services as possible. We develop the mixed integer programming (MIP) model for minimizing cycle time to find an optimal stable timetable for the given line plan. The heuristic iteratively solves the MIP model and applies relaxation measures. We tested the model on the Dutch network. The results showed that the model can generate stable timetables by removing train services from the critical circuit, and also, higher transportation demand can be satisfied by additionally relaxing timetable design parameters.Transport and Plannin

Microscopic Models and Network Transformations for Automated Railway Traffic Planning

This article tackles the real-world planning problem of railway operations. Improving the timetable planning process will result in more reliable product plans and a higher quality of service for passengers and freight operators. We focus on the microscopic models for computing accurate track blocking times for guaranteeing feasibility and stability of railway timetables. A conflict detection and resolution model manages feasibility by identifying conflicts and computing minimum headway times that provide conflict-free services. The timetable compression method is used for computing capacity consumption and verifying the stability according to the UIC Capacity Code 406. Furthermore, the microscopic models have been incorporated in a multilevel timetabling framework for completely automated generation of timetables. The approach is demonstrated in a real-world case study from the Dutch railway network. Practitioners can use these microscopic timetabling models as an important component in the timetabling process to improve the general quality of timetables.Transport and Plannin

Resolving instability in railway timetabling problems

A significant growth of the railway transportation demand is forecasted in the next decades which needs an increase of network capacity. Where possible, infrastructure upgrading can provide extra capacity; although in some cases, this is not enough to satisfy the entire transportation demand even if optimised timetabling is performed. We propose a heuristic model to develop a stable timetable which maximises the satisfaction of transportation demand in situations where network capacity is limited. In case the demand cannot be fully satisfied, the model relaxes the given line plan and timetable design parameters. The aim is to keep as many train services as possible and reduce the level of service minimally. We develop a mixed integer linear programming (MILP) model for minimising the cycle time to find an optimised stable timetable for the given line plan. The heuristic iteratively solves the MILP model and applies relaxation measures. We tested the model on the Dutch network. The results showed that the model can generate stable timetables by removing train services from the critical circuit, and also, higher transportation demand can be satisfied by additionally relaxing timetable design parameters.Transport and Plannin

Railway timetable rescheduling for multiple simultaneous disruptions

Unexpected disruptions occur in the railways on a daily basis, which aretypically handled manually by experienced trac controllers with the support ofpredened contingency plans. When several disruptions occur simultaneously, it israther hard for trac controllers to make trac management decisions, because 1)the predened contingency plans corresponding to these disruptions may conictwith each other and 2) no predened contingency plan considering the combined eects of all disruptions is available. This paper proposes a Mixed Integer Linear Programming (MILP) model that reschedules the timetable automatically in case of multiple simultaneous disruptions occurring at dierent geographic locations. This multiple-disruptions rescheduling model considers the interactions between service adjustments made for dierent disruptions. The combined multiple disruptions rescheduling model is applied every time an extra disruption occurs by considering all ongoing disruptions. Also, a sequential single-disruption rescheduling model is considered to handle each new disruption with the last solution as reference. A case study is performed by assuming two simultaneous disruptions occurring in part of the Dutch railways with 38 stations and 10 train lines operating half-hourly in each direction. By setting 3 minutes as the computation time limit in the considered disruption scenario, the combined approach resulted in less cancelled train services and train delays compared to the sequential approach.Transport and Plannin

A multi-state train-following model for the analysis of virtual coupling railway operations

The increasing need for capacity has led the railway industry to explore next generation signalling concepts such as Virtual Coupling which takes moving-block operations further by separating trains by a relative braking distance, like cars on the road. By means of a Vehicle-to-Vehicle (V2V) communication architecture trains can move in a virtually coupled platoon which can be treated as a single convoy at junctions to improve capacity. This concept however introduces the need for additional safety constraints, especially at diverging junctions, which could make actual capacity improvements insufficient to justify investments. Hence, there is a need to understand capacity performances of Virtual Coupling and potential gains over state-of-practice signalling systems. This paper addresses this need by developing an innovative train-following model that captures operational states and corresponding transitions of trains running under Virtual Coupling. A comparative capacity analysis has been conducted for a portion of the South West Main Line in the UK. Promising results have been obtained, showing that the biggest capacity gains returned by Virtual Coupling relate to operational scenarios normally found in practice with trains having service stops and using different routes.Transport and Plannin