SimRa — Sicherheit im Radverkehr (Safety in Cycling Traffic) is a citizen science and smart city research project developed by TU Berlin that uses smartphone sensor data to identify dangerous locations and situations for cyclists across Berlin and other German cities. Cyclists install the SimRa app on their smartphones, which uses the device's accelerometer, gyroscope, and GPS to automatically detect near-miss incidents, sudden braking events, and dangerous overtaking manoeuvres during regular cycling trips. After each ride, users can review detected incidents, confirm or dismiss them, and add contextual information about what happened. This crowdsourced approach generates a comprehensive, data-driven map of cycling safety hotspots that complements official accident statistics, which only capture incidents that are formally reported to police and therefore significantly underrepresent the true scale of cycling danger. By capturing near-misses and minor incidents that never appear in official records, SimRa provides a much more detailed picture of where and why cyclists feel unsafe, enabling targeted infrastructure improvements. The aggregated, anonymised data is made available to urban planners, transport authorities, and researchers, informing decisions about where to build protected bike lanes, redesign intersections, adjust traffic signal timing, or implement speed reduction measures. SimRa's dataset has already contributed to academic research publications and has been used by Berlin's transport administration and district authorities in cycling infrastructure planning. The project embodies Berlin's smart city principles of open data, citizen participation, and evidence-based governance. It demonstrates how ubiquitous smartphone technology, combined with engaged citizens, can generate valuable urban intelligence at minimal cost. SimRa has expanded beyond Berlin to other German cities and serves as an internationally recognised model for crowd-sourced urban mobility safety analysis.
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