Barcelona has the highest density of cars in the EU. Cutting traffic by 25% could save 200 lives

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Reducing traffic in Barcelona by 25 per cent would prevent 200 premature deaths a year, according to a new study.

The Spanish city has the highest density of cars in the EU at almost 6,000 vehicles per square kilometre. Cutting down on combustion engines is no mean feat, but new research from the Barcelona Institute for Global Health (ISGlobal) shows the life-saving difference it would make.

Barcelona’s air quality improved in 2024 for the second year in a row, thanks to a series of polluting-cutting policies, the city’s air pollution monitoring network said in January. 

Some progress is already being made but ISG’s research imagines a full implementation of the 2018-2024 Urban Mobility Plan launched under former mayor Ada Colau.

“This study focuses on Barcelona, but it also sets an example for other cities to understand the impact that targeted policies can have on reducing air pollution,” says Mark Nieuwenhuijsen, director of ISGlobal’s Climate, Air Pollution, Nature and Urban Health programme.

How would cutting cars save lives in Barcelona?

The researchers worked with the Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), which has developed a technology to model traffic emissions throughout the city and subsequent pollution levels. 

From a baseline set in 2019, they worked out three hypothetical scenarios, each with different levels of traffic reduction. 

The first simulation removed the most polluting vehicles from the roads but didn’t reduce the overall number of private vehicles in the city. This led to a 5.9 per cent drop in nitrogen dioxide (NO2) levels – a gas which increases the risk of respiratory illnesses.

According to the researchers’ model, this would prevent 67 premature deaths a year.

Under the second scenario, a 25 per cent reduction in the number of private cars on the road would result in a 17.6 per cent reduction in NO2 levels, preventing 199 deaths per year. 

Most of the people affected by this change live in the city centre – the area with the highest pollution levels – as well as areas to the north-west.

What difference would electrifying the port make?

Barcelona’s busy ports are a significant source of pollution too, with maritime traffic contributing around 7 per cent of NO2-related mortality in the city.

The Port of Barcelona is planning to electrify its docks by 2030, and ISG’s third scenario looked at the impact of this development alongside a 25 per cent cut in private road traffic.

The result was a 19.4 per cent reduction in NO2 levels and 228 fewer preventable deaths per year. 

Unsurprisingly, this scenario would save most lives in the southern areas of the city, the ones closest to the coast.

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“The study focuses only on the impact of these measures on NO2 levels, but it is hoped that they will also have a positive effect on the climate in terms of reducing greenhouse gas emissions,” says Marc Guevara, leader of the atmospheric emissions modelling team at the BSC.

How has Barcelona been reducing road pollution?

Last year, the Catalan capital reached record low levels of nitrogen dioxide. The Eixample monitoring station, in the heart of the city’s traffic-loaded grid system, reduced its NO₂ levels by nearly 6 per cent.

Authorities attributed this improvement to a variety of factors, including measures to increase the use of public transport – which is cheap but notoriously slow and unreliable.

Low-emission zones have helped limit pollution too, by restricting access for certain polluting vehicles in large parts of the city.

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Also under the Urban Mobility Plan, the creation of ‘superblocks’ has won the admiration of urban planners around the world. This scheme groups together nine city blocks and closes them to through traffic, designing play areas and green spaces to fill these spaces instead.

Barcelona still needs to move faster in clearing up its roads and air, however.

“Although the preventable mortality we estimate is significant, none of the scenarios proposed in our study would be able to comply with the new NO2 limits proposed by the European Union in its new air quality directive, which will come into force in 2030,” says Ana Ramos, ISGlobal researcher and first author of the new study published in the journal Health & Place. 

“This suggests that we must do more and do it more effectively in order to improve the air quality in our city.”

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