Non-exhaust emissions, generated by the wear of brake systems, tires, roads, clutches, and road resuspension, are responsible for a large part of airborne pollutants in urban areas. Brake wear accounts for 55% of non-exhaust emissions and significantly contributes to urban health diseases related to air pollution. A major part of the studies reported in the scientific literature are focused on experimental methods to sample and characterize brake wear particles in a reliable, representative, and repeatable way. In this framework, simulation is an important tool, which makes it possible to give interpretations of the experimental results, formulate new testing approaches, and predict the emission produced by brakes. The present comprehensive literature review aims to introduce the state of the art of the research on the different aspects of airborne wear debris resulting from brake systems which can be used as inputs in future simulation models. In this review, previous studies focusing on airborne emissions produced by brake systems are investigated in three main categories: the subsystem level, system level, and environmental level. As well as all the information provided in the literature, the simulation methodologies are also investigated at all levels. It can be concluded from the present review study that various factors, such as the uncertainty and repeatability of the brake wear experiments, distinguish the results of the subsystem and system levels. This gap should be taken into account in the development of future experimental and simulation methods for the investigation of airborne brake wear emissions.

Tourist areas are one of the most populated parts of cities. Air quality in these spaces is critical as they are more susceptible to the particles emitted by vehicles. The concentration of exhaust emissions around these sensitive locations may cause untreatable health issues for visitors, commuters, and citizens. Heavy-duty vehicles (HVs) are one of the most influential factors creating adverse impacts on air quality. This study proposes a state-of-the-art simulation-based approach to study the relationship between an HV’s speed, its fuel consumption, and its contribution to exhaust emissions in sensitive locations. For this purpose, air pollution and fuel consumption in various scenarios were simulated and compared. The proposed method was applied to one of the most popular tourist areas in Trento (Italy), using VISSIM and EnViVer traffic simulation software packages. The results confirmed the impact of vehicle speed on fuel consumption and the amount of emission. The results showed that a 100-km/h increase in the speed of both light vehicles and HV can increase the NOx and volatile organic compound emissions by approximately 20%. Also, CO emissions and fuel consumption increase by approximately 33% when the HV speed increases from 30 to 50km/h. The emission per seat can be decreased by up to 40% and 27% by 20- and 10-km/h reductions in speed, respectively, together with a 100% increase in the HV percentage. Implementing this proposed method could avoid the unintentional negative impacts of air pollution on susceptible visitors.