The Wait for ERTMS - Keeping Conventional Systems Safe

In the Netherlands, railway safety is largely based on the combination of train detection and ATP by 75Hz Track Circuits. The ATP system (ATBEG) uses the 75Hz signal of the same track circuits. This binds the systems. Replacing the track circuits is only economically feasible when the ATP system (including the onboard ATP equipment) is replaced.75Hz track circuits are relatively simple circuits, using robust components, used since the 1960's and before. To date, 16.000 track circuits of this type are in use, covering over 80 percent of the network.Train detection with track circuits is becoming less reliable. Developments in rolling stock (very smooth running) and rail maintenance (optimal grinding for noise reduction and optimisation of the rail profile to increase the life span ) lead to more difficult shunting of the track. Traction systems are becoming complex and interaction between rolling stock may introduce interference currents that cause risks for reliable detection and ATP.The policy in the Netherlands is to introduce axle counters when ERTMS is installed. With ERTMS, 75Hz ATP is no longer required and thus, track circuits are no longer necessary. The introduction of axle counters will then provide reliable train detection, no longer depending on the shunting of the track.ERTMS is eventually to be installed on the complete main network. However, the rollout will take time. It requires a high budget and the capacity of many signalling engineers to upgrade all lines. It is therefore expected that the full roll-out will take over 30 years. Development of new trains and rail maintenance will continue and may lead to a further decrease in detection performance.ProRail now faces the challenge of keeping the conventional lines safe during the time that ERTMS is not yet installed. A double investment in new systems or additional systems is costly.With an unsolicited proposal in 2012, Movares advised Prorail to develop a new version for the track relay of the track circuit. The ambition for this is to improve reliability and enhance the functionalities by just replacing the track relay and not changing anything else.ProRail embraced this idea and after a business case study, development of the Electronic Track Relay (ETR) started in 2015. A laboratory prototype has been developed as a proof of concept.The ETR enables the life span of track circuits to be extended by 30 years, just by replacing one component in the track circuits. ETR means (A) Functional improvements by means of digital signal processing, by (1) reliable detection, even in case of loss of shunt conditions, (2) improved immunity to near-band interference currents; and (B) Technical improvements, by (1) Easy adjustment of the track circuit and (2) Included maintenance interface for remote monitoring and diagnosticsProRail intends to develop the ETR together with industrial partners leading to a design that will be open source. This leads to an open market and shared knowledge for the railway world.The paper will describe the challenges faced and the solutions we found while developing the prototype of the ETR.