The European Rail Traffic Management System (ERTMS) is a single European signalling and speed control system that ensures interoperability of the national railway systems, reducing the purchasing and maintenance costs of the signalling systems as well as increasing the speed of trains, the capacity of infrastructure and the level of safety in rail transport.
ERTMS comprises of the European Train Control System (ETCS), i.e. a cab-signalling system that incorporates automatic train protection, the Global System for Mobile communications for Railways (GSM-R) and operating rules.
Technical specifications for ETCS and GSM-R are published in the Control Command and Signalling (CCS) Technical Specification for Interoperability (TSI).
GSM-R provides voice communication for train drivers and signallers and provides data communication for ETCS. ERTMS and GSM-R rules are published in the Operation and Traffic Management TSI.
ERA plays the role of system design authority for ERTMS. In that respect, it must establish a transparent process to manage, with the contribution of the sector’s representatives, any system changes.
ERA is requested to identify all errors that potentially could not allow the system to provide a normal service and to publish as early as possible the respective solutions to correct them as well as the evaluation of their impact in the compatibility and stability of the existing ERTMS deployment. This work has been undertaken by ERA in cooperation with the sector and has resulted in a technical opinion (ERA/OPI/2017-2).
Within the scope of this assessment and provided that its recommendations are taken into account, the ETCS baseline 3 MR1 is backwards compatible with ETCS baseline 2.
A second baseline compatibility assessment has checked that:
The second baseline compatibility assessment also includes the analysis of the compatibility between trackside and onboard both within ETCS baseline 3 MR1 and within ETCS baseline 2, in the light of the problem description of the Change Requests included in ETCS baseline 3 R2.
This second baseline compatibility assessment confirms that the ETCS baseline 3 R2 is fully backwards and forwards compatible with the ETCS baseline 3 MR1, i.e. that ETCS baseline 3 R2 vehicles can run a normal service on ETCS baseline 3 MR1 trackside and ETCS baseline 3 MR1 vehicles can run a normal service on ETCS baseline 3 R2 trackside.
ERA organises and processes the Change Control Management (CCM) for the ERTMS specifications and related documents listed in Annex A of the Control Command and Signalling (CCS) Technical Specification for Interoperability (TSI).
A CCM procedure exists under the ERA Integrated Management System. This procedure is based on the former procedure originally approved by the ERTMS Control Group and takes account of the return of experience accumulated over the past years.
Any modification to the ERTMS specification is analysed via a Change Request (CR). CRs can only be submitted in the CCM tool by the representative bodies. More information about the submission of CRs can be found in the restricted ERTMS area.
The use of some ETCS variables requires co-ordination, including the definition of who is assigning new values. Care has to be taken not to assign identical values for different purposes or vice versa. Reasons for this may be functional or safety related.
Based on the functionality behind each variable, a list for the organisations responsible for assigning values to them has been established (see section 188.8.131.52 of Subset-054) and can be classified as follows:
National technical rules (NTRs) are one of the obstacles for the harmonised implementation of ERTMS and thereby, their numbers are to be reduced as far as possible.
The relevant NTRs have to be notified to the European Commission, using NOTIF-IT.
Currently, NTRs can be found at several locations at different national levels, in the ERA Reference Document Data Base (RDD) and in NOTIF-IT. In addition, several Member States have just started to elaborate their NTRs. This situation may create difficulties for organisations applying for a vehicle authorisation.
As a temporary measure, ETCS and GSM-R NTRs are provided below.
Feedback from ERTMS projects shows that ERTMS interoperability constituents and sub-systems contain restrictions and specific conditions of use. The Control Command and Signalling (CCS) Technical Specification for Interoperability (TSI) requires that such information should be provided during the certification process.
Therefore, ERA has developed a template and related guidelines to ensure that the deviations are described in a common and transparent way. The input for the template has to be provided by the Notified Body (NoBo) in collaboration with the applicant.
A control command and signalling system does not brake, i.e. it is not responsible for the braking system of the train, which will do the actual job. ETCS (and also some elaborated legacy systems) supervises both the position and speed of the train to ensure they continuously remain within the allowed speed and distance limits, and -if necessary- it will command the intervention of the braking system to avoid any risk of the train exceeding those limits.
To do so, the ETCS onboard computer must predict the decrease of the train speed in the future, from a mathematical model of the train braking dynamics and of the track characteristics ahead. This prediction of the speed decrease versus distance is called a braking curve.
From this prediction, the ETCS onboard computer calculates in real time braking distances, which will also be used to assist the train driver and to allow him/her to drive comfortably, by maintaining the speed of the train within the appropriate limits.
The ETCS baseline 2 specifications lay down the basic principles for the braking curves and the associated information displayed to the driver, but there is still no harmonised method/algorithm to compute them.
The convergence towards a stable specification of the ETCS braking curve functionality has now been achieved and is reflected in the ETCS baseline 3 specifications.
The ETCS braking curves algorithm consists of a complex set of equations. The Agency has developed a tool, which allows predetermining all the braking distances, as they would be computed by the ETCS on-board equipment. The tool allows capturing all train data (including the correction factor K_dryrst obtained from the Monte Carlo calculation) and trackside, which are relevant to the braking curve calculation and displaying graphically the braking distances so calculated.