Erosion of road markings in Croatia and estimate of contribution to microplastic pollution

Road markings belong to currently irreplaceable elements of roadway infrastructure. Due to degradation by passing vehicles they lose functional properties and then – if not renewed promptly – can become abraded. Upon complete abrasion (erosion), the underlaying pavement can be observed, which permits for quantification of the extent of erosion. This can be used to indirectly measure the contribution of road markings to microplastic pollution – an important current environmental issue. The goal of the study was providing estimate for Croatia, where the climatic conditions and the used materials differ from previously analysed regions. Hence, for such estimation, 95 pedestrian crossings (421 individual ‘zebra’ stripes) were evaluated. Based on the decrease of luminance at the marked areas, average erosion was estimated at 7.4%; however, median erosion of individual stripes was only 1.84%. After combining this data with estimated erosion at longitudinal lines, on average only circa 4.0% of all road marking in Croatia could be considered as being eroded, which is insignificant in comparison with alarming prior reports of >30%. Therefore, knowing the quantity and type of applied road marking materials, it was estimated that approximately 44.0 t of microplastics were annually released in Croatia from this source of pollution. It must be highlighted that grossly negligent maintenance of just 25% of the analysed stripes caused approximately 84% of the estimated microplastic release. Reasonably good maintenance and mild climate in Croatia were contributing to the low emissions quantity; however, the necessity of appropriate renewal schedule and the use of high quality materials must be emphasised.