How do you design a healthier place to live?
“I would prioritise easy, car-free access to everything you need in your daily life"

Two decades of growth has left the city much larger. Like other major cities experiencing growth, Warsaw has developed widespread suburbs. These suburbs often lack essential facilities and access to public transport. 

This makes Warsaw an interesting modelling example for researchers working on urban environments. 

Because how do you design a healthier place to live?

“When you live somewhere, it’s about more than just a roof over your head. You need access to food stores, schools, pharmacies, kindergartens, meeting places, public transport – you name it. If these aren’t available in your neighborhood, you drive to wherever you can find them,” says senior scientist Susana Lopez-Aparicio at NILU.

Transport and fresh air

She and her colleagues at NILU, along with a team of Polish researchers, have investigated how cities can expand in an environmentally sustainable way. 

They were particularly interested in transport emissions and air quality. 

Warsaw was used as a case study, but their findings can also be applied to other cities. 

Suburban sprawl encourages car use

Over the last 20-plus years, Warsaw has experienced an unprecedented period of growth – accompanied by rising housing prices. 

Until recently, the expansion of Warsaw’s metropolitan area has largely taken place without any overarching plan. 

"This has led to a very distinguishable pattern of so-called suburban sprawl. Natural land has been replaced by detached houses, with little room left for amenities and services. We dubbed this a ‘suburban monoculture’ of detached houses,” says researcher Henrik Grythe.

Such sprawling cities encourage more daily car use. Commuting distances increase, leading to more traffic congestion. All of this, in turn, results in rising emissions of polluting gases.

The way a city is designed influences how people travel to their daily destinations. Can you get to work easily and efficiently using public transport? Is your doctor’s office within walking distance? Can your kids safely bike to school? 

All of these factors determine what kind of transportation people use.

Where do people need to go?

With Warsaw as their backdrop, the researchers modelled and evaluated two potential ‘city design’ scenarios. One: continuous sprawl. The other: alternative compact development. 

The two models produced quite different results.

In the continuous sprawl scenario, researchers moved people from the city centre to the suburbs. This resulted in a 47 per cent increase in CO₂ transport emission for the relocated population.

Now, residents also had to rely on cars for commuting and errands. Not only did the model show that they would use their cars more often, but each trip also became longer.

"Perhaps more surprisingly, the traffic in the downtown area didn’t go down much at all. While we couldn’t model everything with enough specific granularity to detail out all effects, we think the fact that there are no proper ring roads is important. Thus, most people living in the suburbs still had to drive through the city centre to get to other parts of town,” says Grythe.

In the other scenario, people were moved in the opposite direction – towards the city centre. This compact development scenario reduced overall emissions from traffic.

Reducing polluting emissions is usually positive. The more pollutants there are in the air we breathe, the more we are exposed to it. However, in this case, compacting the population had a negative effect on human exposure.

“If we increase the population density in the city centre while the pollution stays the same, we just end up with more people being exposed to harmful air quality levels," says Lopez-Aparicio.

In the researchers' models of a compact Warsaw, this is exactly what happened. Even though emissions dropped significantly, air pollution levels were still high in the areas where even more people were now living.

"Thus, the exposure to air pollution went up in the compacted city,” he says.

The researchers also had to account for the fact that if possible, suburban residents prefer to travel into the city centre by car.

When you reduce overall traffic by relocating parts of the suburban population to the city centre, the freed-up space on the road is taken up by an increase in downtown traffic from the suburbs. 

While the city dwellers suffer most of the consequences of air pollution, the people from the suburbs are responsible for the underlying emissions, even in the city centre.

Compact living ‘wins’

The researchers modelled additional traffic measures to see what would make for the ideal urban development.

“In reality, it's of course much harder to force people to move in or out of the city than in our model. In addition to the different city developments, we tried several measures to both reduce emissions and improve the air pollution levels. We improved public transport, limited road capacity to force people to not use cars, we moved workplace centres around – we tried everything we could think of,” says Grythe.

The only thing that worked? Improving public transport. 

Any measure aimed at reducing road network capacity only increased congestion and did nothing to reduce emissions.

Gythe explains that following up suburban expansion by moving workplaces to the suburbs only made matters worse in their model of the suburban sprawl scenario. The study found that all modelled mitigation measures ended up being more effective in the compacted city. 

"So at least within the limits of our scope, any mitigating measure applied to reduce transport emissions will be more efficient in a compact city. So, compaction is where you should start – despite the increased exposure to air pollutants,” he says. 

Design for easy access to everything

Road transport and residential heating are the main causes of air pollution in European cities. 

The researchers believe it is therefore essential to understand how urbanisation, emissions, and air quality related to road traffic affect each other when designing healthier cities.

When asked how they would design a city for optimal air quality, Susana Lopez-Aparicio would go for the so-called hub model, meaning centralised, compact city design.

“I would prioritise easy, car-free access to everything you need in your daily life. If all main services and efficient public transport are available locally, it aids in reducing local air pollution,” she says.

Reference:

Lopez-Aparicio et al. Environmental sustainability of urban expansion: Implications for transport emissions, air pollution, and city growth, Environment International, vol. 196, 2025. DOI: 10.1016/j.envint.2025.109310

This content is paid for and presented by NILU - read more

This content is created by NILU's communication staff, who use this platform to communicate science and share results from research with the public. NILU is one of more than 80 owners of ScienceNorway.no. Read more here.

More content from NILU:

• 

  Fires in tropical forests affect more than just the forests

• 

  Engineer Sam Celentano found 222 grams of gold in a laboratory. What was it doing there?

• 

  Air pollution levels are still too high across Europe

• 

  Researchers have discovered how biological particles affect the clouds over the Arctic

• 

  Smoke from Canada is still coming in over Norway

• 

  Smoke from forest fires in Canada reaches Norway