Road safety systems are critical engineering solutions designed to minimize the effects of traffic accidents and increase the safety of transportation infrastructures. Traditional road safety structures are generally manufactured using steel, concrete and polymer materials. However, manufacturing processes with these materials are high-cost, limited in terms of design flexibility and can lead to material waste. In recent years, rapidly developing additive manufacturing (AM) technologies stand out as an important alternative in the production of road safety systems. AM enables the production of complex geometries and enables the development of lightweight and high-strength structures that can absorb impact energy more effectively. This study focuses on the use of AM methods in road safety systems, examining the performance and applicability of polymer, metal and composite materials. The advantages of AM-produced road safety barriers, traffic signs, speed bumps and shock absorbing structures, depending on the material type, are evaluated. In addition, the advantages offered by AM, such as design flexibility, sustainable production processes and material efficiency, are discussed, and technical challenges and applicability limitations are also discussed. This review evaluates the current and potential applications of AM for road safety systems, providing insights into how this technology can be used more effectively in the future. The findings of the study provide significant contributions towards improving the integration of AM technologies into road safety systems from both academic and industrial perspectives. The findings of the study provide important contributions to the development of the integration of AM technologies into road safety systems from both academic and industrial perspectives. Future research can further enhance the innovative potential of AM in road safety systems, with a particular focus on sustainable material use, design optimization and energy efficiency in manufacturing processes. However, overcoming technical challenges in large-scale applications and compliance with regulatory standards are critical research areas for the widespread adoption of this technology.

While the utilization of waste polymers in asphalt mixtures is widely studied, the specific influence of additive geometry on performance mechanisms remains underexplored. This study presents a multi-scale performance assessment of asphalt mixtures modified with waste Polyvinyl Chloride (PVC) foils. Waste PVC foils were processed into two distinct geometries, “Wiry” and “Random”, and incorporated into mixture at dosages ranging from 5% to 12.5% by weight of bitumen via the dry process. At the macro-scale, Semi-Circular Bending, Hamburg Wheel Tracking, Repeated Creep, and Modified Lottman tests were conducted. At the micro-scale, Scanning Electron Microscopy and EDS analyses were employed to investigate interfacial adhesion. The results demonstrated that the “Wiry” geometry significantly outperformed the “Random” by establishing a three-dimensional reinforcement network. Specifically, the mixture modified with 7.5% “Wiry” PVC yielded the highest Flexibility Index of 24.17, representing a 3.7-fold improvement. Furthermore, this optimum dosage enhanced high-temperature stability and maintained moisture resistance (TSR > 85%), whereas dosages exceeding 10% caused agglomeration and performance loss. Microstructural imaging indicated that the fibrous morphology and calcite-rich surface of the “Wiry” additive facilitate superior mechanical interlocking. Consequently, this study suggests that optimizing waste PVC geometry is as critical as dosage for maximizing the durability and sustainability of flexible pavements.

This study investigates the impact response and energy absorption performance of additively manufactured PLA–geopolymer hybrid composites for potential application in road safety barriers. Hybrid Charpy specimens were fabricated with three different infill densities (20%, 60%, and 100%), combining a 3D-printed PLA outer shell with a geopolymer core. Charpy impact tests were conducted in accordance with ISO 179-1 and ASTM D6110, and the absorbed energy, specific energy absorption, and mass efficiency were determined experimentally. A phase-based analytical model was also used to estimate elastic energy contributions, while fracture surfaces were examined to identify infill-dependent damage mechanisms. To extend the material-level findings to an engineering-scale application, the observed trends were transferred to a New Jersey-type road safety barrier model and evaluated using ANSYS Explicit Dynamics. The results showed that infill density strongly affects fracture behavior and energy dissipation performance, with 60% infill providing the most balanced response in terms of energy absorption and mass/material efficiency. The originality of the present study lies in going beyond a material-scale investigation of the impact behavior of additively manufactured PLA–geopolymer hybrid structures by integrally correlating the experimental Charpy results with a theoretical energy-based framework, fracture-surface observations, and explicit dynamic finite element analysis of a New Jersey-type road safety barrier model.