Simulation Model of Speed Control for the Moving-Block Systems under ERTMS Level 3

The moving-block system under ERTMS Level 3 represents a continuous detection of train positions, and continuous infrastructure-to-train communication. This allows trains to follow one another in smaller space and time headways than possible in fixed-block systems. Trains form platoons with undisturbed headways and uniform speeds in moving-block systems, with improved safety and increased capacity. The dynamics of such train platooning are likely to be critical, as this can give rise to several practical effects, including unrealistic performance demand on braking and traction forces, unstable following and incessant speed fluctuations. Dynamic simulation models can be used to test train control algorithms and design solutions to these problems. This paper presents a discrete-time simulation model of a moving-block railway system. The train control algorithm within the system is formulated as a train-following model. We present a constraint train-following model, based on the concept of an optimal velocity and desired following distance. We provide analysis on the performance of the model, in terms of safety and flow stability.