Despite technological advances to reduce energy and materials use and growing political will to pursue green development, population growth in cities is putting ever-greater pressure on the pursuit of sustainability in urban areas. As cities grapple with ongoing environmental challenges, they also face interactions between environmental pollution and public health risks. A notable example is local air pollution, which has been associated with greater susceptibility to respiratory infections. Growing populations increase the exposure to particulate matter in urban areas, and rising incomes increase the total amount of emissions produced as more people are able to own vehicles.

Non-exhaust particle emissions from road traffic consist of airborne particulate matter (PM) generated by the wearing down of brakes, clutches, tyres and road surfaces, as well as by the suspension of road dust. A growing body of evidence shows that PM emissions have significant implications for human health. Furthermore, the damages to human health caused by PM emissions from road traffic can be disproportionately large relative to other sources of PM emissions, as the highest emission levels tend to be localised in areas with the greatest population density, leading to high levels of exposure. Despite the significant burden of non-exhaust emissions on public health, few public policies target them explicitly.

Emissions of particulate matter (PM) from motor vehicles originate from two main sources: the combustion of fossil fuel, which is emitted via tailpipe exhaust, and from non-exhaust processes including the degradation of vehicle parts and road surfaces and the resuspension of road dust. The airborne particulate emissions generated by these processes are defined as non-exhaust PM emissions.

Emissions of particulate matter (PM) from motor vehicles originate from two main sources: the exhaust from combustion engines and the degradation of vehicle parts and road surfaces. The latter, comprising all airborne particulate emissions generated by vehicle and road wear and the resuspension of road dust, are defined as non-exhaust PM emissions. The proportion of PM emissions from non-exhaust sources has rapidly increased in recent years due to the significant reductions in exhaust emissions over this period, and are now responsible for about 90% of all PM emissions from road traffic (Timmers and Achten, 2016[1]; Rexeis and Hausberger, 2009[2]).

The direct and indirect implications of vehicular emissions on the environment and human health indicate that current transportation systems based on the use of conventional vehicles are unsustainable from social, environmental and economic perspectives. Electric vehicles are widely regarded as a solution to many of the negative impacts of their conventional counterparts. Given their potential to reduce local air pollution and greenhouse gas emissions, consumers, businesses, and governments are increasingly supportive of electric vehicles (Requia et al., 2018[1]), which has led to rising shares of new vehicle sales around the world.

Few policy measures currently target non-exhaust emissions. Two broad approaches can be taken to reduce non-exhaust emissions from road traffic, namely either lowering emission factors or reducing vehicle-kilometres travelled. One solution of the former type would involve changing urban travel altogether by switching to technology that does not rely on friction for acceleration and deceleration (e.g. propulsion via magnets, as is used by Maglev trains). This report does not explore such a fundamental shift, as it is not a realistic possibility for micro-level urban passenger travel in the near term. Exceptions come in the form of regulations regarding brake and tyre material, and mitigating measures such as street washing that are taken in some areas. To the extent that supply-side regulations may require extended approval processes, policy measures that reduce vehicle-kilometres travelled can yield more immediate impacts in terms of mitigating non-exhaust emissions.