Traffic-related non-exhaust emissions, particularly from tire wear and brake wear, significantly contribute to urban road dust pollution and heavy metal accumulation. Despite growing concerns over tire-wear particles (TWP) as a source of microplastic pollution, the influence of road roughness (International Roughness Index, IRI), driving speed, and road slope on TWP generation and heavy-metal deposition remains underexplored. This study systematically investigated these relationships; field measurements were conducted across 57 road segments in Seoul, incorporating IRI assessments, road-dust sampling, and elemental analysis. Roads with IRI >3.0 m/km exhibited 11.9 % higher TWP concentrations than smoother roads did. When normalized by traffic volume (TWP/traffic), the strong correlation between IRI and per-vehicle TWP emissions confirmed that road-surface deterioration amplified tire wear independent of traffic density. Low-speed roads (<25 km/h) accumulated 24 % more TWP than high-speed roads (>40 km/h) did, suggesting that stop-and-go driving conditions enhance mechanical degradation. Downhill segments exhibited 0.2-2.1 % higher magnetic content than uphill segments did due to increased braking forces. This trend aligns with known brake-wear emissions, where Fe-, Cu-, and Zn-rich particles from brake pads and discs contribute significantly to on-road dust pollution. These findings provide empirical evidence linking road conditions, traffic behavior, and non-exhaust emissions, emphasizing the necessity of road maintenance and traffic-management strategies to mitigate TWP and heavy-metal deposition. The study offers valuable data for urban planners and policymakers in developing sustainable road infrastructure and emission-control measures, particularly in the context of Euro 7 regulations targeting non-exhaust emissions.
Keywords: Heavy metal; Particulate matter; Road roughness; Road slope; Tire-wear particles.
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