The first edition of IRS 70727 ‘Railway Application – Track superstructure decision-making’ published in July 2021 is a crucial reference document (International Rail Solution) that aims to:

• establish a guideline to help infrastructure managers and planners make the choice between ballasted track and slab track (ballastless) for new lines and for important upgrades/renewal of existing railway lines in particular circumstance,
• provide key elements for decision-making relating to different solutions for slab track, taking multiple and diverse factors into account.

The UIC is now pleased to publish the corresponding appendices comprising:

• Appendix A (State of the Art for Decision-Making Processes). This provides a complete decision-making tree based on a number of real examples and on benchmark studies performed.
• Appendix B (State of the Art of Ballasted Track Systems). This presents a full state of the art account of the ballasted track system, track components, the evolution of different components (ballast bedding, sleepers, fastening systems and rails); design principles (geometrical, environmental, construction and operational aspects, degradation, maintenance and renewal); conceptual improvements and innovations (continuous welded rail, elasticity contact of intermediate components, under-sleeper pads, geosynthetics, bituminous sub-ballast); and track aerodynamics against ballast pick-up and life cycle cost (LCC) considerations.
• Appendix C (State of the Art of Ballastless Track Systems). This presents a full state of the art account of ballastless track systems; a classification model for these systems and the principle of classification; their description (subsystems of a ballastless track system, codification of the subsystem configuration [A and B, C, D, E], prefabricated element [F], transition zones in the superstructure); design principles (geometrical aspects, mechanical aspects and calculation methods, track stability, reinforcement, environmental, safety, construction and operational aspects, degradation, maintenance and renewal, particularities of high-speed ballastless track systems, interaction with the infrastructure, aspects of train-track interaction); evolution of different components; special technical solutions (floating slab track systems, continuous rail support track systems, low vibration/noise track systems); and life cycle costs (LCC).
• Appendix D (Example of a Case Study). This presents a case study based on methodology and scope; definition of section (cross section and track system); preliminary lay-out design and local physical conditions (preliminary design of earthworks, tunnels and viaducts); the urban environment area; environment impact assessment; budget for main infrastructure elements; operational conditions (line functionality, traffic forecast, traffic offer characteristics and schedule, track possession for maintenance and renewal); characterisation of different available track systems (selected track system, subgrade settlement and related phenomena; track installation maintenance and renewal costs; noise and vibration emission levels; longitudinal track-bridge interaction and other serviceability limit states in bridges; risk of ballast flight ‘pick-up”); suitable track option assessment (analysis of technical and operational effects - technical thresholds, differential life cycle cost analysis).

The IRS 70727 was developed as part of the Track Expert Group’s DESMAN project.

A special mention must also go to all the experts and UIC staff involved in producing this new IRS over the past few years.

Link to the IRS: https://www.shop-etf.com/en/railway-application-track-superstructure-decision-making

Link to the appendices: https://appendices.uic.org/UIC-IRS-70727