VEHICLES¿ NON-EXHAUST EMISSIONS: SETUP OF EXPERIMENTAL APPROACHES FOR ON-ROAD CHARACTERIZATION OF TIRE WEAR AND ROAD DUST PARTICLES

The transition toward cleaner mobility has led to notable reductions in vehicles’ tailpipe emissions; however, non-exhaust emissions (NEEs), particularly those from tire and road wear particles (TRWPs), have emerged as a dominant and under-investigated source of airborne particulate matter. TRWPs are mechanically generated, chemically complex, and highly variable, posing challenges for both environmental monitoring and regulatory standardization. Despite growing scientific interest, no harmonized methodology and setups currently exist to quantify TRWP emissions under representative conditions. Yet, controlled conditions and existing data suffer from limited repeatability, inconsistent particle capture, and insufficient chemical characterization. My PhD studentship has been funded by the PNRR 2021-2027 plan in the frame of Research and Innovation/ Intervention (area: Climate, Energy, Sustainable Mobility) in the specific area of sustainable mobility and co-funded by Pirelli Tyre s.p.a. The research activities have been carried out jointly with other research partners such as CNR-STEMS (Consiglio Nazionale delle Ricerche- Istituto di Scienze e Tecnologie per l’Energia e la Mobilit`a Sostenibili/National Research Council Institute of Science and Technology for Sustainable Energy and Mobility) in Naples and DLR FK (Deutsches Zentrum fur Luft und Raumfahrt Institut fur Fahrzeugkonzepte/German Aerospace Center Institute of Vehicle Concepts) in Stuttgart. In particular, my PhD research was aimed at developing and validating experimental setups and measurement protocols for the reliable quantification and characterization of TRWPs, spanning tire testing laboratory environment, chassis dynamometer, and real-world on-road vehicle tests. The work focused on building feasible, reproducible, and scalable approaches from scratch, which integrate test design, aerosol sampling principles, and instrumentation with physical-chemical characterization techniques. The first part of my work was related to the setup of the TRWP measurement methodology to an industrial flat-track tire testing facility by integrating different aerosol measurement techniques. The study demonstrated the feasibility of TRWP emission capture under dynamic load conditions, enabling high-resolution (1 Hz) particle number-mass concentration characterization. Further chemical characterization was conducted on different samples using SEM-EDX (Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy), revealing metallic constituents and tire markers. The second part of the work was carried out at DLR (where I was hosted for 6months during my Erasmus traineeship). The activity involved the design and comparative assessment of twoTRWP collection systems a nozzle-type and an encapsulated housing on a chassis dynamometer using a BMW i3. The systems were optimized for flow dynamics and sampling efficiency using isokinetic validation and transport loss simulations. Repeatability analyses demonstrated that the housing system offered greater capture efficiency and higher particle number concentrations, especially in the ultrafine range. At the same time, worn tires exhibited more stable emission profiles over multiple test cycles. In the last phase of my PhD work, an on-vehicle sampling setup was developed and applied to outdoor driving conditions, a suitable setup mounted on a Toyota Hilux. The setup included a nozzle-type collection system and a multi-instrument measurement array to quantify particle number and size distributions during indoor and outdoor testing conditions. Results revealed correlations between dynamic driving phases, while system stability and turbulence sensitivity were critically evaluated. Overall, this work presents a comprehensive framework for TRWP measurement methods, spanning from laboratory applications to real-world on-vehicle setups. It provides foundational design guidelines, methodological development, and lays the foundation for future research, benchmarking, and mitigation strategies targeting tire-derived airborne particles.