Statistical Assessment and Temperature Study from the Interlaboratory Application of the WLTP–Brake Cycle

Unrecognized volatile and semi-volatile organic compounds from brake wear

Motor vehicles are among the major sources of pollutants and greenhouse gases in urban areas and a transition to "zero emission vehicles" is underway worldwide. However, emissions associated with brake and tire wear will remain. We show here that previously unrecognized volatile and semi-volatile organic compounds, which have a similarity to biomass burning emissions are emitted during braking. These include greenhouse gases or, these classified as Hazardous Air Pollutants, as well as nitrogen-containing organics, nitrogen oxides and ammonia. The distribution and reactivity of these gaseous emissions are such that they can react in air to form ozone and other secondary pollutants with adverse health and climate consequences. Some of the compounds may prove to be unique markers of brake emissions. At higher temperatures, nucleation and growth of nanoparticles is also observed. Regions with high traffic, which are often disadvantaged communities, as well as commuters can be impacted by these emissions even after combustion-powered vehicles are phased out.

Tracer-Gas-Integrated Measurements of Brake-Wear Particulate Matter Emissions from Heavy-Duty Vehicles

Automotive brake-wear emissions are increasingly important in on-road particulate matter (PM) emission inventory. Previous studies reported a high level of PM emissions from the friction materials of light/medium-duty vehicles, but there are few data available from heavy-duty (HD) vehicles equipped with drum brakes despite their popularity (∼85% in HD vehicle fleet). This study developed a novel tracer-gas-integrated method for brake-wear PM emission measurements and evaluated four HD vehicles on a chassis dynamometer that complied with regulatory exhaust emission testing requirements. Three class-6 vehicles with a similar test weight demonstrated repeatability, with the coefficient of variation in the range of 9-36%. Braking events increased PM concentrations by 3 orders of magnitude above the background level. Resuspension of brake-wear PM also occurred during acceleration and contributed to 8-31% of the total PM2.5 mass. The class-6 vehicles had PM2.5 emissions from a single brake (0.7-1.5 mg/km/brake), generally similar to the level of tail-pipe exhaust PM emissions (0.7-1.5 mg/km/vehicle) of each vehicle. A class-8 vehicle exhibited brake-wear PM2.5 emissions (2.4-3.4 mg/km/brake) significantly higher than the tail-pipe exhaust PM emissions (∼1.3 mg/km/vehicle). This article reports an exceptionally high level of brake-wear PM emissions measured directly from the drum brakes of HD vehicles.

Engine, aftertreatment, fuel quality and non-tailpipe achievements to lower gasoline vehicle PM emissions: Literature review and future prospects

Spark ignition gasoline vehicles comprise most light duty vehicles worldwide. These vehicles were not historically associated with PM emissions. This changed about 15 years ago when emissions regulations forced diesel engines to employ exhaust particulate filters and fuel economy requirements ushered in gasoline direct injection (GDI) technology. These shifts reversed the roles of gasoline and diesel vehicles, with GDI vehicles now regarded as the high PM emitters. Regulators worldwide responded with new or revised PM emissions standards. This review takes a comprehensive look at PM emissions from gasoline vehicles. It examines the technological advances that made it possible for GDI vehicles to meet even the most stringent tailpipe PM standards. These include fuel injection strategies and injector designs to limit fuel films in the engine cylinder that were pathways for soot formation and the development of gasoline particle filters to remove PM from engine exhaust. The review also examines non-exhaust PM emissions from brake, tire, and road wear, which have become the dominant sources of vehicle derived PM. Understanding the low levels of GDI tailpipe PM emissions that have been achieved and its contribution to total vehicle PM emissions is essential for the current debate about the future of internal combustion engines versus rapidly evolving battery electric vehicles. In this context, it does not make sense to consider BEVs as zero emitting vehicles. Rather, a more holistic framework is needed to compare the relative merits of various vehicle powertrains.

Comparative analysis of non-exhaust airborne particles from electric and internal combustion engine vehicles

This paper evaluates the effect of the electrification of the small, medium, and large internal combustion engine (ICE) passenger cars on the levels of total particulate matter (PM). The total mean PM₁₀ and PM_2.5 emission factors (EFs) on urban, rural, and motorway roads are in the range of 26.13 - 39.57 mg km^-1 veh^-1 and 13.39 - 18.44 mg km^-1 veh^-1, respectively, from small to large ICE passenger cars. Correspondingly, the total mean PM₁₀ and PM_2.5 non-exhaust EFs on urban, rural, and motorway roads range from 27.76 to 43.43 mg km^-1 veh^-1 and 13.17 -19.24 mg km^-1 veh^-1 from equivalent small to large electric vehicles (EVs) without regenerative braking. These results show that the total non-exhaust PM from the equivalent EVs may exceed all PM from ICE passenger cars, including exhaust particle emissions, which are dependent mainly on the extent of regenerative braking, followed by passenger car type and road type. PM₁₀ EFs for equivalent EVs without regenerative braking on urban, rural, and motorway roads are all higher than those from ICE cars. As for PM_2.5, most of the equivalent EVs require different extents of regenerative braking to reduce brake emissions to be in line with all particle emissions from relative ICE cars.

The Development of Strategies to Reduce Exhaust Emissions from Passenger Cars in Rzeszow City—Poland. A Preliminary Assessment of the Results Produced by the Increase of E-Fleet

Urban agglomerations close to road infrastructure are particularly exposed to harmful exhaust emissions from motor vehicles and this problem is exacerbated at road intersections. Roundabouts are one of the most popular intersection designs in recent years, making traffic flow smoother and safer, but especially at peak times they are subject to numerous stop-and-go operations by vehicles, which increase the dispersion of emissions with high particulate matter rates. The study focused on a specific area of the city of Rzeszow in Poland. This country is characterized by the current composition of vehicle fleets connected to combustion engine vehicles. The measurement of the concentration of particulate matter (PM2.5 and PM10) by means of a preliminary survey campaign in the vicinity of the intersection made it possible to assess the impact of vehicle traffic on the dispersion of pollutants in the air. The present report presents some strategies to be implemented in the examined area considering a comparison of current and project scenarios characterized both by a modification of the road geometry (through the introduction of a turbo roundabout) and the composition of the vehicular flow with the forthcoming diffusion of electric vehicles. The study presents an exemplified methodology for comparing scenarios aimed at optimizing strategic choices for the local administration and also shows the benefits of an increased electric fleet. By processing the data with specific tools and comparing the scenarios, it was found that a conversion of 25% of the motor vehicles to electric vehicles in the current fleet has reduced the concentration of PM10 by about 30% along the ring road, has led to a significant reduction in the length of particulate concentration of the motorway, and it has also led to a significant reduction in the length of the particulate concentration for the access roads to the intersection.