New study and interactive visualization from the Complexity Science Hub (CSH) highlight the impact of city morphology on average travel distance.
THE STUDY IN A NUTSHELL
- The team built a model that captures key parameters of city shape to create various virtual layouts. The model simulates the commute of thousands of citizens and computes their average travel distance.
- Besides round and centrally compact cities, moderately pyramidal profiles that concentrate high-rise buildings in the center reduce travel distances by 20-25% compared to flat layouts.
- Understanding the dynamics creates opportunities for planning more sustainable urban habitats, especially where cities are still growing.
- The interactive visualization “Cities morphology” and the Cities Morphology Calculator let users change parameters to directly observe the effect on average travel distance.
The world’s future is in cities. It is estimated that by 2050, 7 out of 10 people will live in urban areas (while a recent CSH study suggests that the growth of large cities may be less dramatic than current projections indicate, it still points to continued and substantial urban growth).
Urbanization matters on many fronts, including sustainability: according to the International Energy Agency, cities account for roughly 75% of the global energy use and 70% of greenhouse gas emissions. Of all factors that shape a city’s energy use and emissions, transportation takes a substantial share.
Transportation energy demand scales with the average journey length within the city. This doesn’t only depend on a city’s size, but also on its shape.
Now, a team of researchers led by CSH’s Rafael Prieto-Curiel simulated how urban morphology relates to the distance that people cover when traveling from A to B.
Centrally dense, pyramid-shaped cities minimize travel distance
In their study, the team considered various parameters of urban shape, including whether the city is round or elongated, centrally dense or sprawling. The city profile is another key factor that describes how building heights are distributed across the urban area. Based on this, five distinct layouts emerge: a “pyramid city” (most tall buildings concentrate in the center), a “needle city” (a few very tall buildings in the center), a “pancake” or flat city (uniform height), as well as a “bowl” (most tall buildings towards the periphery), and a “ring” city (only in periphery).
Varying each parameter at a time, the researchers generated a corresponding virtual city layout. For each virtual city, they ran simulations of 100,000 origin-destination journeys and computed the average travel distance.
The results confirm that a compact and round city shape benefits travel efficiency. Elongated layouts that stretch along one axis increase travel distance in a non-linear fashion. Vienna, which was used as a reference for the model, is moderately elliptical and has an average travel distance of just under 10 km. “Dresden, for example, is much more elliptical in comparison,” says Prieto-Curiel. “Due to this difference in shape and despite having fewer people, Dresden has an average travel distance of 13 km, making commutes in the city 30% longer than in Vienna.”
The study also finds that pyramidal shapes are also beneficial. Moderately pyramid-shaped profiles alone can lower travel distances by 20-25% compared to flat layouts, as taller buildings in the center bring potential origin and destination points closer together, thereby yielding substantial efficiency gains.
Why this matters in a world of growing cities
While city morphology is often subject to constraints (geographical, political, and those imposed by past decisions), the study shows that understanding the impact of city shapes creates opportunities for planning more equitable, resilient, and sustainable urban habitats.
This matters especially where cities are growing massively: According to UN projections, Africa will be home to 40% of the world’s population by 2100, and the majority of this growth will take place in large urban clusters. Informed decisions in urban planning will therefore impact the world’s energy demand and the lives of hundreds of millions.
Together with data visualization expert Liuhuaying Yang, the team also published the interactive visualization “Cities morphology” and a calculator that allows users to change key parameters and immediately observe the impact on travel distances—a practical and engaging resource for city planners, policymakers, and the public.
Previous research by Rafael Prieto-Curiel showed that city shape is also a crucial determinant of access to clean water. By 2050, sprawling cities could leave 220 million people without clean water and sanitation.
Find out more here and discover the interactive visualization “Urban Thirst”.
About the study
The study “What is the best shape of a city? Modelling the effect of urban form on travel distance,” by Tobias Batik, Guillermo Prieto-Viertel, Jiaqi Liang, Liuhuaying Yang, Dániel Kondor, and Rafael Prieto-Curiel, was published in Environment and Planning B: Urban Analytics and City Science.
