Train movement under the virtual coupling system: the VCS applications used to increase route capacity and to reduce delay

The Virtual Coupling System (VCS) has been proposed as a new system for controlling trains by building groups of trains into train convoys. The main purpose is to increase route capacity by reducing separation distance between successive trains. This is achieved because successive trains under the VCS are separated only by a relative braking distance; this is much shorter than the separation distance required in the existing Fixed Block Signalling (FBS) and Moving Block Signalling systems (MBS). To achieve high capacity from the VCS, trains in a virtually coupled convoy should keep at a distance as close to the relative braking distance as possible and run at the same velocity for maintaining the distance between them. To date, many approaches have been introduced for controlling trains under the VCS. These approaches can be applied to control trains operating as a train convoy, in which a following train will operate depending on its leading train’s movement. However, they might result in some shortcomings such as lower capacity due to exceeding separation distance, or unsafe and unstable movement that will limit the benefit from the VCS. In this thesis, we propose an approach based on distance and velocity difference control laws and introduce the multiple state movements for simulating train movements under the VCS. The simulated results show that the route capacity is significantly increased compared to the capacity under the MBS. The separation distance between trains when they are in the convoy state is close to the required minimum safe distance under the VCS and obviously shorter than the minimum separation distance required when proceeding under the MBS. This also ensures that trains proceed safely in that the separation distance is greater than the minimum safe distance throughout the operation time period. We also show that trains can proceed smoothly, with a following train catching up with its leading train and joining up into the convoy with stable movement. In addition, the simulated acceleration and deceleration profiles show that they are limited within the realistic range. One problem of the VCS is the loss of capacity when trains pass a junction. Various approaches have been introduced to control trains passing through a junction, but results show that the capacity at a junction is not significantly higher than capacity under the MBS. In this thesis, we also introduce the state movement controlling a train convoy passing over a junction. The simulated result shows that the capacity at a converging junction is increased as trains can operate as a train convoy passing through the junction. This could ensure that trains could operate safely, in which the distance between trains could be extended to at least minimum safe distance required at a diverging junction when they pass the junction. The separation distance between trains under the VCS relies on many parameters such as operating velocity, braking rate, and velocity difference when building a train convoy. So, building a train convoy with different values may result different rates of capacity. 16 parameters that may impact on route capacity are determined. The capacity utilization in terms of number of trains, velocity deviation, timetable heterogeneity, and punctuality (travel time) is also determined for identifying how a parameter impacts on route capacity. According to the simulated results, it is found that building trains into a convoy and transferring them into the convoy state earlier will increase route capacity. There are many solutions such as using a higher velocity difference to build a train convoy, braking by using a higher braking rate, etc. Building trains as a train convoy could not increase route capacity if the number of trains that could proceed along the same route is lower than the maximum number of trains under the MBS. So, the VCS should be used when the number of trains that will proceed along the same route is over capacity under the current signalling system. As we know the number of trains, we could use the VCS approach to create a new timetable. The idea is to merge some trains into a train convoy in order to lengthen the time gap in front of/behind a convoy sufficiently to insert an extra train. In this thesis, the proposed VCS approach is used to manage train timetable. By following this approach, we can identify which trains should be merged as a train convoy, how many trains will be built into the same convoy, and how they are merged into a train convoy. Simulation results show that the time gap in front of and/or behind a train convoy is increased sufficiently to allow an extra train to be inserted safely. Thus, the route capacity in terms of the number of trains could be increased compared to maximum capacity under the MBS. In operating state, a train may be delayed reducing route capacity. In this thesis, we propose the VCS approach to build a delayed train and an impacted train (a train that will decelerate causing delay due to the delay of its front train) together as a train convoy. This will allow an impacted train to proceed with constant velocity until the distance separated from a delayed train is shorter than relative braking distance. So, delay could be prevented or delayed. The simulated results show that secondary delay could be reduced, and it is significantly lower than delay when trains operate under the MBS.