Cycle lanes with minimal traffic impact

While cycling infrastructure promotes sustainability, health, and increased bike adoption, its implementation often sparks controversy due to the need to repurpose car lanes, parking spaces, or public transport routes. With a novel optimization approach that carefully balances the trade-off between bike and car travel times, bike lanes can be allocated such that they have minimal impact on other travel modes—paving the way for a more widely accepted (e-)bike city.

Cycling is a sustainable, efficient, and health-promoting transportation mode, yet its adoption remains limited. This is partly due to insufficient urban infrastructure. But how can we best integrate bike lanes into an existing urban road network?

In the paper “Bike Network Planning in Limited Urban Space,” published in the journal Transportation Research Part B: Methodological, researchers led by Professor Martin Raubal and Nina Wiedemann at the Institute of Cartography and Geoinformation at ETH Zurich introduce a novel optimization method for improving bikeability with minimal impact on other travel modes.

Their approach leverages the concept of Pareto-optimality: When car lanes are transformed into bike lanes, car travel times inevitably increase. The key question is: By how much? Pareto-optimal solutions are the street networks that present the best trade-off between car accessibility and bikeability. To quantify bikeability, the authors use the concept of “perceived bike travel time.” Studies have shown that cyclists perceive dedicated bike lanes as faster.

To optimize the bike network, they developed a linear programming approach. This method improves over traditional approaches by proposing networks that have both lower car travel times and lower perceived bike travel times. In a case study, the scalability of the algorithm is demonstrated by designing a radically new bike network for the entire city of Zurich, where the perceived bike travel time decreased by 43%.

This research is part of the E-bike City project, a multidisciplinary initiative at the ETH-Department of Civil, Environmental and Geomatic Engineering exploring the effects of a radically changed urban road space with priority on cycling. Planning a suitable bike network is a core challenge in this project. The proposed optimization framework enables planners to design e-bike cities that maximize public acceptance as they minimize disruptions to car travel.