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As cities work to achieve their emissions reductions goals and implement changes for more sustainable transport systems, the focus has long been on reducing vehicles’ exhaust emissions. However, a less visible but increasingly significant source of pollution has persisted: non-exhaust emissions (NEE). Non-exhaust emissions are particles that get released into the air from parts of the vehicle outside of the engine, such as brake wear, tyre wear, road surface abrasion and the resuspension of road dust.
Unlike exhaust emissions, which have been tightly regulated for years, NEEs remain largely unregulated despite their growing contribution to particulate matter in the air and the serious health problems that they cause, such as asthma, cardiovascular disease and premature death. Cities, where dense traffic and population converge, are now facing the challenge of addressing this often-overlooked pollutant.
Across Europe, and especially in leading cities like London, efforts to curb transport-related emissions have shown progress. Investments in low-emission zones and electrification of fleets have been bringing down exhaust emissions – but as exhaust-emissions reduce, the problem of NEEs becomes a larger and larger share of transport emissions.
Recognising this shift, EIT Urban Mobility launched the Targeted Innovation Call, with a specific focus on NEEs. Currently, two different projects are underway to address and create positive impact on the reduction of NEEs. One project, a partnership with The Tyre Collective, Eurometropole de Strasbourg, and Ringway introduces a patent-pending electrostatic filter (TC05) that captures particulate matter from tyre and road wear directly at the source of the vehicle before it can enter the atmosphere.
Additionally, EIT Urban Mobility, in collaboration with Transport for London (TfL) and the Greater London Authority, have crafted a report with e:misia, entitled Study on non-exhaust emissions in road transport in order to assess and address the prevalence of NEEs in London, with the goal of providing recommendations that are both relevant and helpful to other large European cities.
Electrification and NEEs
One aspect of the study looked at the impacts of electrification on NEEs. While the electrification of vehicle fleets undoubtedly works to reduce carbon dioxide and nitrogen dioxide, there have been concerns as electric vehicles (EVs) often heavier than their internal combustion counterparts due to large batteries.
While heavier vehicles lead to greater tyre and road surface wear, the study also found that EVs drastically reduce brake wear. Unlike conventional vehicles, EVs use regenerative braking systems that reduce reliance on traditional friction brakes. The study found that while tyre wear might increase slightly with heavier EVs, brake wear can decrease by up to 83%, offsetting part of the NEE burden. The net impact is still positive, but nuanced, and thus requires cities to consider a holistic view when planning their mobility transitions.
Modal shift matters
One finding from the study’s scenario simulations was that encouraging a shift in transport modes, from private vehicle usage to public transport or active mobility, has a significantly larger impact on reducing NEEs than electrification alone.
In the case of London, the study found that modal shift is up to five times more effective in the reduction of particulate emissions than merely replacing combustion vehicles with electric ones. This finding may be obvious, as reducing car use altogether reduces all forms of vehicle-related emission, exhaust and non-exhaust alike. Fewer cars means less tyre wear, less brake use and less road dust moving through the air; a clear conclusion albeit an important one.
This insight strengthens the case for cities to double down on active mobility infrastructure, public transport investment and policies that disincentivise car dependency. The study also suggests that electrification should be paired with broader strategies incentivising modal shift in order to achieve the maximum financial benefits.
Tools for urban decision-making
To help cities move from analysis to action, EIT Urban Mobility, in collaboration with Transport for London, Greater London Authority, and e:misia has also created Power BI simulation tool to translate emissions data into strategic insights. The tool allows stakeholders to visualise the impact of different interventions, from electrification and modal shifts to technical material upgrades, on NEE levels across different boroughs and population segments.
Although developed with data from London, the underlying methodology can be adapted to any urban context. By inputting their own transport and emissions data, other cities can simulate how similar interventions might perform in their unique environments with hopes of encouraging pan-European learning and a supra-national harmonised approach to NEE reduction.
Recommendations at local, national and EU levels
Tackling non-exhaust emissions requires coordinated actions at urban, national and supra-national (European) levels, supported by technical innovations and strategic policies. Thus, from a policy and planning perspective, addressing NEEs also involves making informed decisions about materials and technologies. For example, the study’s cost-benefit analysis revealed that using higher-quality brake and tyre materials with increased wear resistance can significantly cut NEE without requiring major infrastructure changes. Although these materials are more expensive upfront, their longevity and environmental benefits make them a cost-effective choice over time.
These kinds of technical interventions, such as material upgrades, often fall under the remit of national or EU-level regulation rather than city governance. Cities can support their adoption by piloting these materials in public transport fleets or infrastructure projects, but widespread implementation will depend on broader policy changes and market availability.
At the same time, cities have the power to reduce NEEs through strategic urban planning and behavioural policies. Shaping travel demand by improving public transport, expanding active mobility infrastructure, and disincentivising heavy internal combustion vehicle use through financial penalisation like high parking fees can reduce the number of vehicles on the road and the total distance travelled. Additionally, emissions modelling tools, such as the Power BI platform developed for London, offers cities an opportunity to test the expected impact of different policies before full deployment, helping to optimise decision-making based on local conditions.
For national and EU-level policymakers, the study recommends enabling and accelerating these efforts. While establishing clear regulatory standards for NEEs, especially regarding tyres and brakes, is critical, investment in research and innovation is also necessary for improvement without compromising safety or affordability. A harmonised approach to emissions reporting and data-sharing across cities would also help to build evidence needed for effective regulation. Strategic funding streams at the European level could enable cities to scale their initiatives and share best practices across borders.
Confronting the next emissions challenge
As cities make advances toward reduced exhaust emissions, NEEs are emerging as the dominant source of vehicle-related air pollution in cities. However, EIT Urban Mobility’s recently published study shows that this new challenge can be met with access to the right data, tools, policies and partnerships. While electrification offers promising progress, cities, countries and the EU as a whole need to coordinate efforts to enable the systemic shift in how people move through cities.
