cf. city flows - Comparative visualization of urban bike mobility

cf. city flows is a comparative visualization environment of urban bike mobility designed to help citizens casually analyze three bike-sharing systems in the context of a public exhibition space.

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Three high-resolution screens show the space of flows of New York City, Berlin, and London through visualizing the bike-sharing systems of these global cities. By showing the flow of multiple cities side by side, we can compare their extent and dynamics. Tracing urban movements accentuates different urban structures, and contrasts grid-plan cities like New York with historically grown cities such as Berlin. It also enables us to observe and dwell on similarities and differences in various bike-sharing systems. With our visualizations we want to understand the pulse of urban mobility and create portraits of a city defined by its transient dynamics.

Citywide view showing bike trajectories in Manhattan in the morning.

Cycling is increasingly recognized as critical component of future urban mobility. Riding a bike is largely independent of other traffic and unaffected by road congestion, and has health and environmental benefits. In the last few years, many cities around the world installed bike-sharing systems in order to stimulate casual use of bicycles by locals and visitors alike. We used data from these systems to visualize various aspects of bike-sharing mobility.

cf. city flows is an installation that combines multiple visualizations of bike-sharing journeys in three cities. It applies established mapping and visualization techniques within a highly aestheticized framework in order to animate visitors to engage with urban mobility.

Visualization Design

cf. city flows has three viewing modes, all visualizing trips of rented bikes, but focusing on different levels of spatial and temporal granularity of cycling mobility:

  • The citywide view aggregates all trajectories of bike-sharing trips for a given day and animates the trails for trips at a given time.

  • In the station view only the bike trips to and from a selected station are shown, allowing the distinction between incoming and outgoing.

  • A small-multiple view visualizes spatiotemporal patterns for three selected stations each in an exploded view that separates incoming from outgoing and morning from afternoon/evening trips.

Visitors can switch between these viewing modes resulting in smooth transitioning into the next scene. Each view shows an animation moving through the day and highlights bike trips of the current time with a fading trail for better visibility. The views of all three screens are temporally and spatially coordinated, showing the same time of day and having the same map scale.

Lacking actual GPS tracks, the trip trajectories are rendered as smooth paths of the calculated optimal bike routes (see Methodology for details). As different trajectories still share some segments of the street network, aligning the bike movements with actual roads makes it possible to compare the accumulated use of urban infrastructure.

Details on Data, Methodology, Interactions and Design Considerations

Visit our project page for more information and images.


Nagel, T., Pietsch, C., Dörk, M. Staged Analysis: From Evocative to Comparative Visualizations of Urban Mobility. In Proceedings of the IEEE VIS Arts Program, VISAP’16 (upcoming)

In the Press


Project by Till Nagel and Christopher Pietsch, Urban Complexity Lab, FH Potsdam.

We wish to thank our colleagues from the Urban Complexity Lab for all their support and feedback. We especially thank Samira Akhavan, Andrea Biedermann, and Christian Münch for designing and constructing the exhibit furniture. This work was supported in part by HERE.