European GNSS Navigation Safety Service for Rail
Background & Objectives
Localisation systems, also known in railway as signalling systems, are used to ensure train safe traffic, i.e. no collision nor derailment. Historically, signalling systems were specifics to each area of operation. Interoperability across Europe was achieved through the ERTMS norm, under ERA patronage.
The current ERTMS system relies on train on-board odometry coupled with trackside detection systems to get trains speed and track occupancy computed on the trackside. To augment railway performances and sustainability, trains should continuously compute their position and speed on board (ERTMS level3), making use of EGNSS hybridised localisation systems.
In this new paradigm, a concept of integrity for train safe localisation is needed, modelled on what was already done in other domain, e.g. EGNOS in civil aviation.
The European Commission (EC) is defining the roadmap for the long-term evolution of the EGNSS (i.e. EGNOS and Galileo) programme, including new services and new capabilities.
An EGNSS-based rail safety service would address the need for an accurate and trustable train localisation.
The EGNSS-R project is composed of five main sequential tasks, which are segment analysis, integrity concept design, service definition, acceptance analysis and roadmap production. Each of these tasks includes interactions and a validation session with a working group called ERGO (Experts in Rail for EGNSS Operational use), which comprises representatives of railway operators, railway industry and GNSS industry.
The segment analysis aims at studying Positioning, Navigation and Timing (PNT) applications for rail critical market, electing the most suitable options from a technical and economical perspective. At the end of this task both realistic architecture for a hybridised train localisation system and technologies to perform its integrity function shall be found, and their possible evolution analysed.
The project will then move on to the integrity concept design. This phase will include use case definition, quantitative and qualitative trade-offs on sensor coupling, high level risk analysis and preliminary safety apportionment. The concept will be as agnostic as possible regarding the architecture of the localisation system, in order to be compliant with ERTMS and RCA requirements (The RCA initiative advocates for trackside requirements agnostic w.r.t. technology. It is formed of railway operators and is interfaced with the EUG (ERTMS User Group) body).
During EGNSS-R first iteration the following tentative structure for the localisation system has been defined: (click the image for full view)
Test requirements will be written as preliminary directives for integrity service tests to be done outside the scope of the study.
With final segment analysis and mature integrity concept issued, the EGNSS-R team will then work on an EGNSS integrity service proposal for the rail and associated roadmap. Dissemination means and in particular EDAS-like services together with their requirements will be studied.
Finally, the acceptance analysis will build on the previous tasks work to assess whether EGNSS-R designs could suit railway PNT ecosystem. Both integrity concept and service definition together with roadmap recommendations will use this feedback to refine their outputs.
Work performed & results
The European Global Navigation Satellite Systems (EGNSS - EGNOS and Galileo), are a cornerstone of the European transport policy. They provide ubiquitous accurate and robust navigation solutions to users across multiple transport domains as well as in other non-transport related segments.
GNSS was also recognized by the railway community as one of the key game changers that could improve efficiency of train localization within the future ERTMS evolution. The EGNSS-R study will help clarifying whether a railway EGNSS-based safety service shall be created.
In addition, the integrity concept proposal will feed ERTMS standardisation processes on GNSS introduction in the railway domain and define the steps for rail multi-sensor localisation system certification.
The results will be added at a later stage.
Disclaimer: The project results represent the views of the consortium. They do not necessarily represent the views of the European Commission and they do not commit the Commission to implementing the results.