Enhancing Road Safety with Smart Road Marking Paints: Self-Cleaning and Thermochromic Capabilities

Road markings (RMs) are infrastructure elements positioned to guide road users, regulate traffic, and enhance road safety. Significant advances in materials technology, such as the use of several types of paints and retroreflective materials, have contributed to improving the durability and day and night visibility of RMs. However, challenges in this field still remain, and recent developments have focused on using smart materials to incorporate innovative functionalities into RMs. Notable examples include semiconductors, which can photo-oxidize surface pollutants and provide self-cleaning properties, and thermochromic materials, capable of changing color at specific transition temperatures (TTs), offering visual feedback on pavement surface conditions. In this context, the objective of this study was to develop RM paints with self-cleaning properties (to enhance visibility and durability) and thermochromic properties (to indicate the potential presence of ice or snow on asphalt pavements). For the self-cleaning RM paint, different amounts of TiO₂ were incorporated into a water-based acrylic RM paint. The self-cleaning ability was assessed using CIELAB colorimetry to monitor the degradation of a model pollutant under UV light irradiation. For the thermochromic RM paint, thermocapsules with a TT equal to the freezing point of water (0 °C) were incorporated into a water-based acrylic RM paint. The thermochromic behavior was analyzed by the CIELAB system while the paints were exposed to negative and positive temperatures. The results showed that the self-cleaning RM paint achieved pollutant degradation capacity up to 3.2 times higher than the reference paint. The thermochromic RM paint demonstrated the ability to change to a pinkish color at temperatures below 0 °C, reversibly returning to the original white color at positive temperatures. Both properties showed potential to enhance road safety by improving visibility and providing visual feedback on usage conditions.