ProxiCycle: Low-Cost Sensor System Tracks Close Car Passes to Improve Bike Route Safety

Researchers at the University of Washington have developed ProxiCycle, an affordable and compact sensor that fits into a bicycle’s handlebar and helps identify unsafe roads for cyclists. The system records when cars pass within four feet of a cyclist, which is considered dangerously close. Data is then transmitted via Bluetooth to a smartphone app. The team tested the system over two months with 15 cyclists in Seattle, logging over 2,000 close passes. Results showed a strong correlation between these close passes and known accident hotspots as well as areas with perceived low safety. This approach provides a real-time, scalable method to map risky routes and could significantly aid city planning and bike safety applications like Google Maps or Strava. Researchers validated the system using video analysis and sensor comparisons in controlled and real-world environments. The device costs under $25 to build, making it an accessible safety tool for wide deployment. Future improvements aim to include other risk factors, such as parked car doors opening. With broader adoption, ProxiCycle could contribute to safer, more informed cycling infrastructure and encourage more people to ride bikes by minimizing risk.