Thermoplastic road markings are vital for traffic safety but have high environmental impacts due to energy-intensive production of binders, pigments, and glass beads. Recycling end-of-life thermoplastic materials can reduce reliance on virgin resources, yet long-term field performance data are scarce. This study evaluates the durability and performance of formulations with 10 and 30% mechanically milled recycled content after 12 months of natural outdoor exposure and under accelerated xenon-arc UV ageing. Field trials under Nordic traffic and climate conditions assessed retroreflectivity (R_L), luminance coefficient (Qd), chromaticity coordinates, and skid resistance in line with European standards. Initially, the 10% recycled formulation met all requirements, while the 30% fell below the Qd threshold. After 12 months, R_L decreased mainly within wheel tracks due to traffic wear, whereas Qd increased for both formulations, especially the 30%. Chromaticity coordinates remained within the white region, indicating stable colour, and skid resistance increased over time. Accelerated xenon-arc ageing caused minor Qd reductions and slight shifts in x, y chromaticity coordinates, reflecting UV-induced binder oxidation without mechanical wear, bead loss, or surface contamination. Comparison of natural weathering in combination with traffic load and artificial ageing highlights the limited ability of UV-only laboratory testing to replicate field-relevant degradation. Overall, the results suggest that thermoplastic road markings containing 10–30% recycled material can maintain performance levels approaching those of conventional materials, although some parameters remained close to or slightly below specified thresholds. While further validation is needed, the findings indicate potential for the use of recycled thermoplastic road markings and highlight the need for comprehensive ageing assessments. By demonstrating the technical viability and performance of recycled thermoplastic road markings, this study supports the potential contribution of such materials to SDGs 9, 11, 12, and 13. These relate to more resilient infrastructure, improved road safety, efficient use of resources, and reduced environmental impacts through the adoption of circular economy approaches, subject to further validation through long-term and life-cycle assessments.