An Algorithm for Braking Curve Calculations in ERTMS Train Protection Systems

This paper describes how the European Railroad Transportation Management Systems (ERTMS) standard for train protection, European Train Control System (ETCS), includes several advanced features for predicting safe speed from a number of target locations ahead of the train. The braking system can have a different braking capability in different speed segments. The area in front of the train can contain a number of targets with different target and release speeds. The area in front of it is also segmented according to the gradients, in a way which is independent of the targets. The variables that shall be input to the braking curve algorithm therefore have three dimensions. Since permitted speed shall be calculated, rather than time to intervention, square roots are needed for the calculations, which require some computational power. The article suggests an algorithm where the gradients and the targets are combined in one table. This makes the input variable area two-dimensional instead of three-dimensional, which simplifies calculations and reduces the necessary number of square root calculations.