Today, the economic crisis and the restriction of energy resources and deposits have given a new perspective to railways as a transport system that is friendly to the environment and contributes to sustainable development more than any other terrestrial transport medium. Moreover, the need to reduce transport costs, both of people and goods, with more cost-effective use of the product, ‘transport’, leads to the development of combined transport. Combined transport – road–railway and railway–waterway – is often considered a panacea. It can combine the capabilities of diverse methods of transport in an ideal way, assigning the appropriate role to each means: railway and barges for long-distance transport; road transport for local distribution. The railways can only benefit from the development of combined transport and, on the whole, they must play the leading role in their development. In this perspective, high-speed railways should be the core of a future combined transport network in order to secure speed, frequency of services, line capacity and prices. It is emphasised that the optimum use of high-speed railways is the connection of major cities that are several hundred kilometres apart. This should be accomplished, if possible, with no intermediate stops in order to attract new customers.
The design and construction of the super- and substructure of a modern railway line plays an important role in the stressing of the infrastructure and, as a result, in the maintainability of the geometry of the track. Given the fact that the huge expense of operating and maintaining the railway infrastructure constitutes the main disadvantage of railways, its reduction is of high priority. Given the fact that deterioration in the quality of the track geometry is exponentially related to the stressing of the track, investigation and development of new techniques and technologies for the design and construction of the super- and substructure of a modern railway line (i.e. a high-speed railway line) needs to address these matters. Technology development has created research needs, especially in the last few years, in terms of modelling of specific materials and construction techniques, laboratory testing, or even in situ characterisation for quality control needs or track performance evaluation purposes.
This special issue of International Journal of Pavement Engineering highlights recent developments in track super- and substructure as well as more theoretical approaches to the performance and loading of the track. At the same time, it aims to provide an insight into existing experience and motivation to explore new aspects of the scientific area of high-speed railway infrastructure. It includes high-quality, peer-reviewed, scientific or technical contributions devoted to several topics related to the development of new technologies in the design and construction of track superstructure, investigation of the mechanical properties and laboratory testing of track super- and substructure, modelling of the material used and of the track itself, substructure in situ non-destructive investigation, structural analysis and loading aspects and mechanisms, performance assessment aspects, case studies, as well as the implied economic aspects related to high-speed railway infrastructure.
In closing this introduction, I would like to thank the Journal's Editors-in-Chief, Tom Scarpas and Imad L. Al-Qadi, for their support. I would also like to thank all the international authors who contributed to this special publication. Their high-end scientific work is greatly appreciated. Last but not least, I would like to acknowledge the reviewers for their time and effort in improving each paper.