Battery-powered buses have grown into a familiar fixture on urban roads across Europe, their numbers climbing steadily over the past several years. A small electric-plug symbol displayed on their windows makes these vehicles straightforward to identify across urban areas such as Brussels and Madrid.

Roughly 300,000 people across EU member states lost their lives in 2023 due to air quality that fell short of thresholds set by the World Health Organization. Road transport — spanning freight vehicles, privately owned cars, and public transit alike — accounts for roughly 14% of the fine particulate matter (PM2.5) loading measured across urban areas throughout Europe.

Urban and suburban areas together are responsible for roughly one in every four tonnes of transport-related greenhouse gas output recorded across European Union member states. A target of reaching climate neutrality across all member states has been set by the bloc for the year 2050, with reducing greenhouse gas output from transport by ninety percent against 1990 baseline figures forming a central pillar of that strategy.

Michela Le Pira, an assistant professor of transportation at the University of Catania in Italy, has described phasing out exhaust emissions — the gases and particles that combustion engines release during operation — as potentially "the easiest strategy to improve public transport," a view she has advanced in the context of road traffic's contribution to air quality deterioration across European cities, where the majority of the continent's population resides.

A joint investigation cataloguing sustainability pledges made by municipal authorities and transport operators across 33 European cities — drawing on more than 100 reports and sources spanning over ten years of public transit and emissions records — tallied 148 discrete commitments in total. Motorised public transport forms the core of the study's scope, with cycling, walking, taxis, ride-sharing services, and e-scooters all falling outside its boundaries.

Of all the capital cities belonging to EU member states, Copenhagen has moved the furthest toward eliminating exhaust emissions from its public transport network, transitioning the vast majority of its bus fleet away from combustion engines and onto battery-driven electric vehicles. Diesel-powered vehicles still dominate bus networks in cities such as Rome, Lisbon, and Nicosia, where more than nine in ten buses rely on that fuel and rail-based options — metros and trams combined — cover fewer than one in ten vehicles across those public transport systems.

One in five buses operating across EU capitals and a selection of other cities runs on electric power. From 2021 to 2025, that fleet category expanded by 55 per cent, adding roughly 1,234 additional units to active circulation. Drawing on EU financing, numerous urban transit networks expanded their rosters of zero-emission and alternative-fuel buses from 2021 onwards.

Fleet composition data shows diesel-only vehicles have been losing ground over time, yet they remain more numerous than those powered by alternative fuels. Among the 31 cities where data were available, more than half of the bus fleets in 20 of them still rely on conventionally powered vehicles.

A data analyst at Transport & Environment, a non-profit focused on cleaner transport, noted that battery-electric buses represent one pathway toward lowering air pollution at street level. Switching to electric vehicles across the bus network carries the potential to trim both operational expenditure and ambient noise levels, while simultaneously cutting exhaust emissions and improving local air quality. Baierl noted that the benefit grows further when a city generates its own power supply.

Purchasing electric buses carries a steeper price tag than acquiring their diesel-powered counterparts. Hydrogen-powered buses represent a further option in the zero-tailpipe-emission category, though their day-to-day running costs tend to run higher than those of battery-electric vehicles.

Among European cities, Brussels moved away from conventional diesel fleets at a relatively early stage, opting for hybrid vehicles in their place. Brussels is working to convert its vehicle fleet to electric power, and Baierl noted that pinpointing which technology will ultimately prove viable remains an open question.

Of all the sectors tracked under EU climate accounting, road and rail movement stands out as the one area where emissions have not fallen back to the levels recorded in 1990 — a gap that puts it at odds with the bloc's stated goal of cutting transport-related output by 90% before 2050. Of the EU's member states, only a small number are currently positioned to meet that target, with the remainder falling well short of where they need to be.

Figures drawn from the Carbon Disclosure Project — a non-profit organisation — show that across the ten largest EU capital cities, buses, trams, and metro systems together account for well over one in four journeys on a typical day. Forty-nine percent of Stockholm residents fall into that category, compared with just eleven percent in Ljubljana, the Slovenian capital.

Of the pledges on transport sustainability examined, just four cities put forward binding commitments to eliminate tailpipe emissions from buses or their wider public transit networks.

Yannis Papadimitriou's home lies about 85 kilometres from Athens, a capital that pollution mortality figures place among the EU cities recording some of the higher death tolls linked to poor air quality. He commutes by rail and has described the choice as deliberate — preferring electrically powered public transport, with trains standing out in his view for their safety record, low environmental impact, and journey speed, though trains, trams, and metros account for only part of the urban network, where buses remain more numerous and diesel propulsion still predominates across many city systems.

Poul Kattler once made a regular journey into work from his home roughly 15 kilometres outside Copenhagen, in the northern reaches of Europe. Since leaving the workforce, he spends a good deal of time riding the bus alongside his grandchildren. Kattler noted that while Copenhagen's public transport network runs almost entirely without fossil fuels — a single biomethane bus aside — the new metro line brings its own environmental concerns, particularly during the building phase, which places a heavy burden on natural resources.

Pollution tied to automobiles reaches across a broader spectrum of sources than exhaust pipes and engines alone. Friction generated at the wheel and brake contact points sends fine particulate matter into the surrounding air each time a vehicle decelerates. Upstream carbon sources — power generation and fuel refining among them — extend the overall climate burden attributed to the transport sector.

Tighter restrictions on exhaust emissions have applied to buses and other fossil-fuel-powered road vehicles across the EU dating back to 1992. Data published by the European Environment Agency placed the reduction in fine particle output from buses and heavy-duty vehicles at 92 per cent over the course of 2022. Tyre wear from road vehicles has pushed non-exhaust particulate output up by 58 percent over a span of twenty years, a trajectory tied to the growing weight of passenger cars.

Electrifying bus and rail fleets addresses only part of the urban emissions challenge, Le Pira noted, arguing that the deeper obstacle lies in persuading residents to leave private vehicles behind in favour of shared transit networks. CDP figures show that passenger cars handle, on average, just over one-third of all journeys made within the largest EU capital cities.

Discounted fares for group travellers — students among them — paired with measures that discourage car dependency, such as low-emission zones, together offer a dual-pronged approach to growing ridership while easing pressure on private vehicle use. Le Pira's research examines ways to make public transport both more efficient and more attractive to urban residents — for instance, through integrated systems that let people move seamlessly from cycling to rail — while Baierl expressed the view that cities where car use is not a necessity for everyone tend to offer a higher quality of life.