Editorial of “Sustainability of Transport Infrastructures”

Sustainability in transport infrastructures has become a key priority for governments, industries, and researchers worldwide. Alongside their substantial environmental repercussions, efficient transportation systems contribute significantly to societies’ economic and social progress. Recent international goals, such as the United Nations Sustainable Development Goals [1], have underscored the need to reduce the carbon footprint of transportation. Organisations like the European Union [2] have also set ambitious targets for lowering greenhouse gas emissions. These objectives have pushed the industry to adopt greener technologies, use materials more efficiently, and develop innovative strategies to enhance the resilience and longevity of transport networks [3].

In the context of pavement construction, sustainability efforts focus on reducing the consumption of natural resources, minimising energy use, and lowering the environmental impact of infrastructure projects. These goals have been achieved through the increased integration of bio-based binders [4] and advanced design techniques, along with the adoption of circular economy principles, which promote the reuse and recycling of materials to reduce waste and extend the life cycle of resources used in construction [5]. Moreover, self-healing materials have shown promise as an innovative approach to enhance the durability of pavements by allowing minor damage to repair itself, potentially reducing maintenance needs and extending infrastructure lifespans [6]. Sustainable transport infrastructures are also essential for enhancing social equity, as they improve accessibility and connectivity, particularly in underserved communities [7]. Resilience to climate change is another critical aspect [8]. With the increasing frequency of extreme weather events, it is crucial to design transport infrastructures that can withstand such conditions, ensuring long-term performance [9,10].

However, despite these advancements, several challenges remain. One of the primary issues is the durability and long-term performance of sustainable materials under varying environmental conditions, such as temperature fluctuations and moisture exposure [11]. Despite the increasing adoption of sustainable practices, the ability of these materials to endure different environmental stresses is still not fully understood. Additionally, although life cycle assessment (LCA) is widely recognised as a valuable tool for evaluating environmental impact [12], its practical application in projects remains limited [13]. More robust policies are needed to address these gaps and ensure the consistent implementation of LCA and other sustainable practices across different regions and transportation networks [14].

This collection of research papers on “Sustainability of Transport Infrastructures” brings together studies addressing these critical challenges. The articles span a range of topics, including decarbonising transport systems, utilising recycled and bio-materials in pavement construction, and conducting life cycle analyses of infrastructure solutions. Taken together, these contributions provide a solid foundation for understanding the current state of sustainable transport infrastructure and offer pathways to address existing knowledge gaps.

A significant focus of this volume is the increasing use of recycled materials in pavement construction in alignment with the principles of the circular economy. Research shows that incorporating recycled asphalt pavement, reclaimed concrete aggregates, and other industrial by-products, such as steel slag, can significantly reduce the environmental footprint of road construction. In addition to maintaining or improving the mechanical properties of pavements, these materials help reduce reliance on virgin resources and thus lower construction costs [15]. In summary, using recycled materials supports both environmental sustainability and economic efficiency by promoting the circular use of resources.

Decarbonisation in transportation is another central theme in this Special Issue. Several articles examine how technologies such as warm mix asphalt (WMA) and alternative binders contribute to reducing carbon emissions. For instance, WMA enables lower production temperatures, thus cutting fuel consumption and greenhouse gas emissions during asphalt production. These studies highlight practical solutions already implemented in real-world scenarios, demonstrating how they can significantly reduce the carbon footprint of transport infrastructure.

Life cycle assessment is also a crucial research theme presented here. LCA enables a comprehensive evaluation of environmental impacts throughout the entire lifespan of a transport system, including stages such as material extraction, production, construction, maintenance, and eventual disposal or recycling. Several contributions in this issue illustrate how LCA can effectively compare the environmental performance of different materials and maintenance strategies. Consequently, these insights hold significant value for policymakers, enabling them to make well-informed decisions about which infrastructure solutions are the most sustainable.

Looking ahead, several promising directions for research and development stand out. For example, bio-based materials, such as bio-binders derived from waste products, offer great potential for reducing the environmental impact of pavement construction [16]. However, further research is needed to evaluate the long-term performance of these materials under real-world conditions. Additionally, the emergence of smart infrastructure systems presents another exciting avenue for exploration. Integrating sensors and monitoring technologies into pavements makes it possible to collect real-time data on road performance [17]. These data could then optimise maintenance schedules, extend infrastructure lifespans, and reduce the need for resource-intensive repairs [18]. In combination with sustainable construction practices, these technologies could transform how transport networks are built and maintained.

Moreover, policy frameworks must also evolve to support the adoption of sustainable materials and practices. Technological advancements are essential, but strong policy measures are equally necessary to encourage the use of greener technologies and ensure compliance with sustainability standards [19]. Policymakers can find valuable guidance in the research presented in this volume. Indeed, it demonstrates how sustainable practices can be effectively implemented and highlights the benefits of adopting a life cycle approach to decision-making.

The contributions to this Special Issue offer a comprehensive view of the current state of sustainable transport infrastructure. By addressing key challenges, such as using recycled materials, reducing carbon emissions, and implementing life cycle assessments, the research offers theoretical insights and practical applications to guide future infrastructure projects. As the transportation sector continues to evolve in response to environmental, social, and economic pressures, collaboration between researchers, engineers, and policymakers is essential. Over time, these endeavours will pave the way for the emergence of technically viable and more sustainable transport solutions.

Future research will be crucial in advancing these initiatives, particularly in bio-material development [20], smart infrastructure, policy integration, circular economy principles, and digitalisation of construction processes [21]. The integration of artificial intelligence (AI), data mining, and building information modelling (BIM) also offers promising pathways in sustainability assessments [18]. For instance, AI and data mining can enhance performance monitoring and predictive maintenance [22], allowing for optimised resource use and more sustainable pavement management. Additionally, combining BIM with life cycle assessment (LCA) enables more precise sustainability analyses by providing detailed insights into material use, energy consumption, and environmental impacts across the infrastructure life cycle [23]. By continuing to explore these avenues, society will move closer to achieving truly sustainable transport infrastructure that meets the needs of both present and future generations.