Assessment of Urban Public Transport Sustainability in Europe

Greener buses and cleaner fleets are reshaping public transport across Europe. However, questions remain about whether cities are progressing quickly enough to meet their zero-emission goals. An electric plug icon on their windows makes them easy to spot in cities like Brussels and Madrid. Electric buses have become increasingly common on Europe's streets in recent years. Michela Le Pira, assistant professor of transportation at Italy's University of Catania, states that removing tailpipe emissions from combustion vehicles may be the simplest strategy to enhance public transport. Most Europeans reside in urban areas, where road transport negatively impacts air quality. In 2023, nearly 300,000 deaths across the EU were attributed to air pollution levels exceeding the World Health Organization's (WHO) recommended thresholds. Of all fine particulate matter (PM2.5) concentrations in European urban areas, approximately 14% originate from road transport, which includes public, private, and freight transport. Additionally, towns and cities contribute nearly a quarter of the European Union's transport greenhouse gas emissions (GHG). DW and the European Data Journalism Network evaluated over a decade's worth of data from more than 100 reports and sources on public transit and its emissions, identifying 148 sustainability commitments by local authorities and transport operators in 33 cities across Europe. The analysis focuses on motorized mass transit, excluding bikes, pedestrians, taxis, shared vehicles, and e-scooters. The EU aims to become the first climate-neutral continent by 2050, with a key component being a 90% reduction in transport-related GHG emissions from 1990 levels. According to DW's analysis, Copenhagen is the only EU capital that has nearly electrified its entire bus fleet, as its vehicles do not have combustion engines and therefore do not produce tailpipe emissions. In cities such as Rome, Lisbon, and Nicosia, more than 90% of buses still operate on diesel, and metros and trams comprise less than 10% of their public transport fleet. Although cars continue to dominate European streets, Martin Baierl, data analyst with Transport & Environment, an advocacy non-profit for clean transport, notes that electric buses are one method to reduce local air pollution. EU funding has allowed many cities to expand their electric and alternative fuel bus fleets since 2021. Electric buses now make up 20% of the total fleet in EU capitals and selected cities, with their numbers increasing by 55% between 2021 and 2025, representing an addition of 1,234 vehicles on the road. The number of diesel-only buses has been declining, although they still outnumber those running on alternative fuel. In Brussels, an early adopter of hybrid buses, the city is currently working to electrify its fleet, albeit at a slower pace. Baierl commented on the uncertainty of what the optimal technology will be in the future. Hydrogen-powered buses, which also produce zero emissions, are noted to be more expensive to operate than electric buses. Transportation remains the only major sector where greenhouse gas emissions exceed 1990 levels, despite the EU's goal of a 90% reduction by 2050. On average, public transport, including buses, trams, and metros, accounts for over a quarter of trips in the ten largest EU capitals, according to recent data from the non-profit group Carbon Disclosure Project (CDP). In Stockholm, the share is 49%, while in Ljubljana, the smaller Slovenian capital, it is 11%. DW's analysis of transport sustainability pledges reveals that only four cities have explicitly committed to achieving zero emissions in buses or all public transport. Yannis Papadimitriou, who lives 85 kilometers (about 53 miles) from Athens, the EU capital with the highest air pollution mortality risk, uses commuter rail, which he believes should be promoted more. He stated, "For me, it is a very conscious choice to use electric public transport, especially trains, which are the safest, most environmentally friendly, and quickest way of transport." While trains, trams, and metros operate on electricity, buses are more prevalent within city boundaries, and many urban areas still rely heavily on diesel. In Northern Europe, 15 kilometers from Copenhagen, Poul Kattler, now retired, takes the bus more frequently with his grandchildren. Despite Copenhagen's nearly fossil-fuel-free public transport system, the expansion of the metro, which is responding to the city's growth, presents its own challenges. Kattler remarked that the construction phase of the new metro line is extremely environmentally demanding. When considering construction emissions, he noted that the CO2 balance would be poor for the metro at present. However, Le Pira stated that the long-term benefits of a new metro line in reducing CO2 emissions outweigh its construction-related emissions. Combustion or exhaust emissions are not the sole contributors to transport pollution; indirect emissions from electricity generation or fuel production also add to transport's CO2 footprint. Non-exhaust particle matter is released from brakes and wheels when vehicles slow down. Since 1992, buses and any vehicles running on fossil fuels in the EU have been subject to stricter emissions standards. According to the European Environment Agency, fine particle emissions from buses and heavy-duty vehicles dropped by 92% in 2022. However, overall road transport non-exhaust emissions from tire wear have increased by 58% over two decades, as cars have become heavier. With few exceptions, EU member states are not on track to achieve a 90% reduction in greenhouse gas transport emissions, as envisioned by the EU's 2050 target. Zero-emission public transport is a step toward decarbonizing urban transport and meeting GHG reduction goals. The next challenge is to encourage people to reduce car usage. Le Pira stated, "If we talk about sustainable mobility in general and not only clean public transport, the main problem is the model shift from private cars to public transport." On average, private automobiles account for over a third of transport in the largest EU capitals, according to CDP data. Implementing cheaper ticket prices for groups, such as students, and creating disincentives for car use, like low-emission zones, are two complementary strategies to attract more passengers while reducing private transport. Le Pira's research focuses on how public transport can be made more efficient and appealing for city dwellers, such as by integrating transport modes where individuals switch from bikes to trains. This solution could be particularly relevant for smaller cities where cars remain the primary mode of transport. Cities with effective public transport systems tend to be more attractive. Baierl noted, "Cities where not everybody has to use a car are just more livable." Edited by: Gianna-Carina Grün and Sarah Steffen. DW's data team contributed research to this project. For data, code, and methodology behind this analysis, see this GitHub repository. More data-driven stories from DW can be found here. This project is a collaboration among several media outlets in the European Data Journalism Network in the context of Chat Europe. Project lead: DW. Contributing partners: Voxeurop, Denik Referendum, EUrologus, OBC Transeuropa.