New index ranks 917 European cities on urban design for health and well-being

Smaller cities tend to show better environmental quality and a higher overall score, while large metropolitan cities perform better on urban design and sustainable transport indicators

Barcelona Institute for Global Health (ISGlobal)

Facebook

X
BlueskyMessageWhatsAppEmail

The Barcelona Institute for Global Health (ISGlobal), a centre supported by the ’la Caixa’ Foundation, has unveiled a new tool: the Healthy Urban Design Index (HUDI). The HUDI is a composite index that evaluates 917 European cities based on 13 indicators connected  to peoples’ health and well-being and divided into four domains: urban design, sustainable transport, environmental quality and green space accessibility. The HUDI is the result of scientific work published in The Lancet Planetary Health. The data for all cities is publicly available on https://isglobalranking.org/hudi/.

In order to make the cities comparable, they have been grouped into five categories according to the number of inhabitants: large metropolitan, metropolitan, medium and small-sized cities and small towns. The 13 indicators assessed include urban compactness, housing density, walking, cycling and public transport infrastructures, air pollution levels, capacity to mitigate and manage heat, and accessibility of green spaces. The index assigns a score between 0 and 10 for each of the indicators analysed and establishes a combined HUDI score. 

Small cities lead the HUDI

Generally, the category with the highest HUDI scores is small-sized cities, which includes all European cities with a population between 50,000 and 200,000 inhabitants. Pamplona (Spain), Geneva (Switzerland) and Harlow (UK), all small-sized cities, lead the HUDI scoring across all categories with scores of 6.8, 6.65 and 6.64, respectively. “The HUDI score differences are often only very small. However, the HUDI shows tendencies and none of the 917 cities achieves a score of 7 or higher out of 10, which gives us an idea of the room for improvement in promoting health and well-being through urban design in Europe," explains Federica Montana, researcher at ISGlobal and lead author of the study.

Large metropolitan cities generally scored better on indicators of urban design (housing density, compactness, mid-rise development and permeability) and sustainable transport (walking and cycling opportunities and number of public transport stops), particularly those in Northern Europe and some in Spain. In contrast, smaller cities show better environmental quality (air pollution, green space and lower urban heat island effects), with higher scores on better air quality and heat mitigation indicators, particularly in Northern Europe.

Differences between Western and Eastern Europe

“One of the trends we observed is that the lowest HUDI scores tended to be concentrated in Eastern European countries such as Romania, Bulgaria and Poland. Conversely, it is in Western European cities, with notable concentrations in the UK, Spain and Sweden that we find the highest scoring cities”, says Natalie Mueller, ISGlobal researcher and co-author of the study. 

Not a final ranking

“The HUDI is not intended to be a final ranking of cities, but rather a first approach using only open spatial data to see how European cities of all sizes perform and compare in terms of providing a healthy urban design to their residents”, says Mark Nieuwenhuijsen, director of ISGlobal's Climate, Air Pollution, Nature and Urban Health programme. “Cities of similar size often face similar challenges and opportunities and providing a high spatial resolution of the indicators and combined HUDI scores can help to pinpoint problems and develop targeted  intervention strategies. Our HUDI is a work in progress and we invite the research, urban planning and policy communities to develop this work further in the future and make other relevant indicators available”, Nieuwenhuijsen adds.  

Top cities by category

The cities with the best HUDI scoring in each category are Madrid (Spain), with a score of 6.04 in large metropolitan cities; Lisbon (Portugal), with a score of 6.09 in metropolitan cities; Bilbao (Spain), with a score of 6.35, in medium-sized cities; Pamplona (Spain), with a score of 6.8, in small-sized cities; and Campobasso (Italy), with a score of 6.02, in the small towns cluster.  

Large metropolitan areas (more than 1.5 million inhabitants)

Total rank	City	Country	Score
39	Madrid	Spain	6.04
148	Barcelona	Spain	5.67
407	Vienna	Austria	5.29
421	London	United Kingdom	5.01
560	Rome	Italy	5.08

Metropolitan areas (500,000 to 1.5 million inhabitants)

Total rank	City	Country	Score
27	Lisbon	Portugal	6.09
54	Stockholm	Sweden	5.96
88	Athens	Greece	5.86
111	Glasgow	United Kingdom	5.79
125	Seville	Spain	5.76

Medium-sized urban areas (200,000 to 500,000 inhabitants)

Total rank	City	Country	Score
10	Bilbao	Spain	6.35
21	A Coruña	Spain	6.14
24	Edinburgh	United Kingdom	6.10
25	Southampton	United Kingdom	6.10
30	Móstoles	Spain	6.08

Small urban areas (50,000 to 200,000 inhabitants)

Total rank	City	Country	Score
1	Pamplona	Spain	6.80
2	Geneva	Switzerland	6.65
3	Harlow	United Kingdom	6.64
4	San Sebastián	Spain	6.51
5	Stevenage	United Kingdom	6.46

Small towns (less than 50,000 inhabitants)

Total rank	City	Country	Score
45	Campobasso	Italy	6.02
272	Ibiza	Spain	5.47
372	Przemysl	Poland	5.35
385	Santurtzi	Spain	5.32
482	Igualada	Spain	5.18

Methodology

The Healthy Urban Design Index assesses 917 cities from 26 European countries, including the United Kingdom, and it has been developed using open data sources, including remote sensing data, OpenStreetMap and EU and government open datasets. 

The team defined 13 indicators that scientific evidence links to physical and/or mental health and grouped them into four key domains: urban design, sustainable transport, environmental quality and accessibility to green space. For each of the indicators, a reference value was defined based on previous studies or recommendations from experts or international organisations. For example, for the air pollution indicators, the recommendations of the annual average values of particulate matter PM2.5 and nitrogen dioxide (NO2) established by the WHO were used as a reference. For those indicators for which there was no reference value, the value of the city with the best result was used as a reference.

Once the data for all the cities had been obtained for each of the 13 indicators, they were compared with the target value and converted to a score between 0 and 10 depending on the result. The HUDI scores were calculated by applying weights to the 13 indicators and were subsequently used to rank cities within their respective city clusters.

The team hopes to improve the HUDI in the future by including other relevant indicators in the context of urban health, such as socioeconomic indicators, transport modal share, or access to and diversity of services and amenities. “The use of all open source data is an important first step. We are making the codes available and hope that cities can use the evidence to understand the links between urban planning and health. The HUDI helps cities not only see the indicators at the city level but also at high spatial resolution, which is important for equity as there can be large differences across neighbourhoods”, says Carolyn Daher, co-author of the study and coordinator of the ISGlobal Urban Planning, Environment and Health Initiative.

“The HUDI is a useful tool and also a call to action for cities to look at the data and distributions, and use their own data to validate findings, define targeted interventions strategies, and contribute with better data to improve the indicators and mapping in the near future”, concludes Natalie Mueller. 

Instructions for accessing the HUDI website

• Address: https://isglobalranking.org/hudi/
• Temporary password: ISGlobalHUDI2025

The IDUS pages will be made public once the embargo is completed.

Reference

Federica Montana, Natalie Mueller, Evelise Pereira Barboza, Sasha Khomenko, Tamara Iungman, Marta Cirach, Carolyn Daher, TC Chakraborty, Kees de Hoogh, Alice Battiston, Rossano Schifanella, Mark Nieuwenhuijsen. Building a Healthy Urban Design Index (HUDI): how to promote health and sustainability in European cities. The Lancet Planetary Health, June 2025.

---

Journal

The Lancet Planetary Health

Article Title

Building a Healthy Urban Design Index (HUDI): how to promote health and sustainability in European cities

Article Publication Date

12-Jun-2025

 

A stress memory effect in olivine at upper mantle pressures and temperatures

Ehime University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Intermediate earthquakes occur in the subducting slabs at depths of 50-300 km. Hypocenters of intermediate earthquakes form seismic zones.

view more 

Credit: Tomohiro Ohuchi, Ehime University

The Kaiser effect, which is known as a stress memory effect, predicts that seismic events occur only when the previous maximum stress is exceeded. Therefore, the Kaiser effect has been applied for the estimation of the magnitude of ‘in situ’ stress on crustal rocks in the community of geotechnical engineering (including forecasting earthquakes). Geodetic observations have revealed that the time dependency of seismicity synchronized with inflation/deflation of a volcano is well explained by the Kaiser effect. However, the Kaiser effect has only been tested at room temperature in laboratories. Here, we performed deformation experiments on natural olivine at high pressures and high temperatures via a state-of-the-art technology large-volume deformation apparatus combined with a microseismicity monitoring technique. We have successfully confirmed a stress memory effect (corresponding to the Kaiser effect in a broad meaning) in strongly deformed olivine at high pressures and high temperatures. The observed memory effect could be effective in the seismic zones of subducting slabs.

A cubic pressure medium (pink) is surrounded by six anvils. Transducers, which are used for the detection of P-waves, are pasted on the rear side of each anvil.

Differential stress and strain increased during the deformation periods (white areas). Differential stress decreased when the deformation was halted (stress-relaxation periods: blue areas). Radiation of acoustic emissions (AEs) occurred during the deformation periods, though AEs ceased during the stress-relaxation periods. These results show the manifestation of the Kaiser effect. However, radiation of AEs proceeded at higher strains (> 0.2) even though the differential stress was below the maximum value (i.e., breakdown of the Kaiser effect).

Credit

Tomohiro Ohuchi, Ehime University

---

Journal

Geophysical Research Letters

DOI

10.1029/2025GL114960 

 

Cost effectivities analysis of perovskite solar cells: Will it outperform crystalline silicon ones?

Shanghai Jiao Tong University Journal Center

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

• Current manufacturing cost of perovskite solar modules is calculated as 0.57 $ W−1 much higher than that of the silicon solar cells.
• Cost Effectivities analysis indicates that materials cost shares 70% of costs, and capital cost and other cost share nearly 15%, respectively.
• The cost of perovskite solar modules has the potential to outperform crystalline silicon under conditions of 25% efficiency, lifetime of 25 years, and cost reduction of materials and equipment, etc.

view more 

Credit: Yingming Liu, Ziyang Zhang, Tianhao Wu, Wenxiang Xiang, Zhenzhen Qin, Xiangqian Shen, Yong Peng, Wenzhong Shen, Yongfang Li, Liyuan Han.

The commercialization of perovskite solar cells (PSCs) has garnered worldwide attention as the next generation of photovoltaic (PV) technology. With their high efficiency and potentially low manufacturing cost, PSCs are expected to revolutionize the renewable energy market. However, the current manufacturing cost of perovskite solar modules is calculated as 0.57 $ W-1, much higher than that of silicon solar cells. Now, Professor Liyuan Han from Shanghai Jiao Tong University, along with researchers from Wuhan University of Technology and other institutions, present a comprehensive cost-effectiveness analysis of PSCs, offering valuable insights into their potential to outperform crystalline silicon solar cells.

Why Cost Effectiveness Matters

• Current Cost Analysis : The manufacturing cost and levelized cost of electricity (LCOE) of PSCs are estimated as 0.57 $ W-1 and 18–22 US cents (kWh) -1, respectively. Materials cost accounts for 70% of the total cost, while capital cost and other costs each account for nearly 15%.
• Potential for Cost Reduction : Sensitivity analysis indicates that improving efficiency, yield, and reducing materials cost can significantly lower the cost of PSC modules. Under conditions of 25% efficiency, 25-year lifetime, and cost reduction of materials and equipment, PSCs have the potential to outperform crystalline silicon solar cells.
• Long-Term Cost Targets : To achieve cost parity with crystalline silicon modules, it is essential to refine the fabrication processes, develop stable inorganic transport materials, and precisely control material formation and processing at the microscale and nanoscale to enhance charge transport.

Innovative Strategies for Cost Reduction

• Improving Efficiency and Yield : Enhancing the efficiency and yield of PSC modules is crucial for cost reduction. For example, improving the yield from 50% to 90% can significantly reduce the cost from 0.571 to 0.324 $ W-1. However, even with high efficiency and yield, the cost of PSCs remains higher than that of crystalline silicon modules.
• Reducing Materials Cost : The cost of materials, especially FTO glass, ITO, and C60, accounts for a large proportion of the total cost. Developing new transparent conductive substrates with lower costs and using cheap inorganic electron transport materials, such as SnO2 and TiO2, are effective ways to reduce materials cost.
• Optimizing Equipment Investment : As manufacturing capacity expands, equipment investment per 100 MW can be reduced. However, the impact of equipment investment on cost reduction is relatively small, as capital cost only accounts for a small proportion of the total cost.

Future Outlook

• Short-Term Target (Scenario 1) : Achieving 20% efficiency and 90% yield within 4–5 years through the extension of current technologies is possible. However, the module cost (0.24 $ W-1) is still higher than that of crystalline silicon modules, so new markets such as mobile electronic devices, toys, see-through devices, and indoor applications should be sought for profitability.
• Long-Term Target (Scenario 2) : PSCs can obtain a cost similar to that of crystalline silicon modules under the coordination of over 25% efficiency, 99.5% yield, 40% materials cost reduction, 50% equipment investment reduction, and 30% electricity cost reduction. Achieving a lifetime of 25 years is also essential for PSCs to have a competitive LCOE.
• Research Directions : To reduce the LCOE of PSCs, several research issues need to be addressed, such as improving production yield, enhancing module efficiency and stability, developing cheap electron transport layer (ETL) and transparent conductive oxide (TCO) materials, reducing vacuum processes, and optimizing the structure of modules.

Perovskite solar cells have shown great potential to outperform crystalline silicon solar cells in terms of cost-effectiveness. However, significant efforts are still needed to improve efficiency, yield, and stability, as well as to reduce materials and equipment costs. Stay tuned for more exciting breakthroughs in the commercialization of perovskite solar cells!

---

Journal

Nano-Micro Letters

DOI

10.1007/s40820-025-01744-x 

Method of Research

Experimental study

Article Title

Cost Effectivities Analysis of Perovskite Solar Cells: Will it Outperform Crystalline Silicon Ones?