It Is How You Build Them: Attractivity of Separated and Mixed-Use Cycling Infrastructure in Bologna Using Long-Term Time Series

Implementing effective cycling mobility requires infrastructure that enhances safety and reduces travel time. A common metric for tracking progress is the total length of dedicated cycling infrastructure. However, this does not always correlate with increased cycling usage. For instance, in Italy (2008–2015), cycling infrastructure grew by 48%, but ridership remained unchanged. Design quality and behavioral and contextual factors all influence this dynamic. This study analyzes a 16-year time series (2009–2024) of monthly cyclist flows surveys in Bologna, Italy. It focuses on flows, gender, and bike lane usage. It represents the most detailed and longest series of its kind in the country. The findings show a positive correlation between infrastructure growth (meters per inhabitant) and cyclist flows, though this weakened significantly after COVID-19 and the extensive introduction of non-exclusive bike lanes on mixed-use roads from 2020. Regression analyses reveal that new bike flows per new meter/inhabitant of infrastructure were 3 times greater before 2020. This study identifies two likely causes: the insufficient perceived safety of the newly introduced mixed-traffic lanes from 2020 and the lack of attractivity of cycling for the female population, as highlighted in the decreasing trend in the usage of bike infrastructure by female riders after 2020.