Meet the ITU researcher paving the way for a better bicycle infrastructure in cities

Associate professor in Data Science at the IT University of Copenhagen, Michael Szell, studies human movement on a large scale among other things to improve conditions for bicyclists in major cities. He is co-author of a ground-breaking paper on human mobility published in the scientific journal Nature.

Computer Science Department Research big data data science

Written 27 May, 2021 12:58 by Theis Duelund Jensen

Associate Professor at ITU, Michael Szell, has been interested in human mobility for most of his scholarly career. The effect of human movement on our interactions and societal development is a focal point of his research which has examined everything from massive multiplayer online games to ride sharing platforms.

Yesterday, marked the culmination of nine years’ work when the esteemed scientific journal Nature published a research paper Michael Szell has co-authored entitled “The universal visitation law of human mobility” in which the authors present a new law for determining population movement based on data from major cities including Boston in the US, Lisbon, Porto, and Braga in Portugal, Dakar in Senegal, Abidjan in Ivory Coast, and Singapore.

Accounting for time

- Using mobile phone data, we have been able to devise a law about how people move around in cities. We have found that humans move along a curve explained by our law. If we know one point on this curve, we can determine all the other points on the curve as well. In other words, by measuring how many people have moved to a certain place, we can infer how many people have moved to other places, says Michael Szell.

That may sound very abstract, but the model devised by Michael Szell and his colleagues may have very significant practical consequences. City authorities will be able to make accurate predictions about population movements and improve on infrastructure and traffic safety, and businesses can get a better handle on where to attract customers and place shops. Those are only a few out of myriad possibilities.

Røde og blå bjergformationer af data på tredimensionelt kort Data visualisation from "The universal visitation law of human mobility"-project (SOURCE: Wanderlust)

What sets the universal visitation law of human mobility apart from, for instance, the gravity model of migration, based on Newton’s law of gravitation, and the radiation law for human mobility, also based on a physics theory, is that the former takes the temporal aspect into account as opposed to focusing solely on the spatial dimension as the latter two.

- Up until now, models have not taken time into consideration. Previously, researchers would only consider the distance a person travels and not the frequency or when the distance was traversed. That was not technologically possible. With datasets as fine-grained and complex as mobile phone data is that is now possible. We studied these datasets in aggregate and found a very distinct law that can describe human movement in space and in time, says Michael Szell.

The website Wanderlust, made by MIT’s Senseable City Lab of which Michael Szell was a member, shows the model’s movement data based on temporal and spatial parameters. The website is beautifully constructed with interactive components visualising, among other things, popular places in Boston as blue and red-capped mountain peaks made up of individual dots representing people.

Improving infrastructure for bicyclists

One way to use the new model is to apply it to one of Michael Szell’s other research areas: bicycle infrastructure. Environmental concerns and public costs are two of a million reasons why bicycling infrastructure should be improved everywhere, but Michael Szell’s reasons spring from personal experience.

- I started biking to work when I was working on my postdoc at MIT and living in Boston. Taking my bike was a lot faster than taking the bus, but the bicycle infrastructure in Boston is a regular death trap. Many bicyclists are killed in traffic. They put up white painted bikes called “ghost bikes” as memorials whenever a bicyclist has been killed in traffic, and I would see a lot of them on the streets. Cycling is the fastest and best way to move around a city, but it is also the most dangerous way. It should not be like that. That is what got me interested in improving conditions and working in the field.

Recently Michael Szell has started working with Danish bicycle organisations like Supercykelstier and Cyklistforbundet. The objective is to identify the missing links in the Copenhagen bicycle infrastructure. By drawing on his expertise in analysing mobility data and using tools from network science to look at the bicycle network and the network of streets, Michael Szell and his associates calculate and measure where the most significant gaps in the infrastructure are located. These gaps are referred to as disconnected components, and in Copenhagen, there are around 300 disconnected components.

- A connected component is a part of the network that allows you to reach one point from another. Disconnected components means that there are gaps between the components. Although, Copenhagen has a very well-developed bicycle network there are still many gaps between components. If you go from one point to another point in the city by bike, odds are you will not be able to use bike lanes all the way, says Michael Szell.

Health and economy

Even though, 300 disconnected components sounds like a high figure, Copenhagen still has one of the best bicycle infrastructures in the world. Michael Szell has also found that city officials are very interested in his work and the City of Copenhagen is very forthcoming with infrastructure data from among other things its cycling strategy which has a similar goal of improving the city for bicyclists. The goal for Michael Szell and his associates is to help the city prioritise spending on new bike lanes.

In Copenhagen, there is a lot of openness to improving bicycle infrastructure, but in general more and more cities are getting there because of the economic benefits, according to the researcher. Building bicycle infrastructure is cheap and efficient. For short and medium distances bicyclists move faster than car drivers, they take up less space on the street, and you do not need to account for costly parking spaces.

- If you make a cost-benefit analysis, bicycling also improves the general level of health in the population. When people exercise every day costs are cut in the healthcare system, says Michael Szell.