A research team from the University of Washington has developed an innovative system called ProxiCycle, designed to make cycling safer and smarter. This low-cost handlebar-mounted sensor detects when a passing car comes closer than four feet (1.2 meters) to a cyclist, logging each incident via a connected smartphone app.
The data collected during two months of testing in Seattle – involving 15 cyclists and over 2,000 recorded close passes – revealed a strong correlation between those locations and known accident-prone areas. Researchers believe that scaling this system could help cities identify high-risk streets and design safer bike routes.
How the system works
ProxiCycle’s sensor fits neatly into a bicycle’s left handlebar. It consists of a 3D-printed plastic housing containing two distance sensors and a Bluetooth antenna, transmitting data directly to the rider’s phone. The sensor costs less than $25 to build, making it accessible for large-scale use.
The device’s algorithm can distinguish between a passing car, another cyclist, a pedestrian, or a tree, minimizing false readings. Before field deployment, researchers tested the system under controlled conditions, followed by real-world trials with GoPro cameras to verify its accuracy.
Turning individual rides into collective safety data
Lead researcher Joseph Breda, a PhD student at the Paul G. Allen School of Computer Science & Engineering, explained:
“Experienced cyclists know which streets feel safe, but that knowledge is hard to share. We wanted a simple way to capture it and make it useful for everyone.”
In a survey of 389 Seattle residents, participants across all experience levels identified the threat of cars as the top barrier to cycling. Most said they would eagerly use a navigation map based on real safety data, but such data has so far been scarce.
A tool for smarter, safer mobility planning
ProxiCycle’s results showed that close-pass events are a stronger indicator of road safety risks than current perception-based methods used by policymakers. With its low cost and high accuracy, the system could become an essential tool for urban mobility planners, helping to build data-driven, cyclist-friendly cities.
As cities worldwide aim to promote sustainable and active mobility, innovations like ProxiCycle could bridge the gap between technology, safety, and better cycling infrastructure – encouraging more people to ride with confidence.
