Getting a Better Handle on Bike Safety

It has often been said that one of the best ways to learn is through your mistakes. There are some fairly clear exceptions to this proverb, however. You would not want to learn by making mistakes in skydiving, for instance, where you have little room for error. Cycling through city streets may not be quite as unforgiving as jumping out of an airplane, but getting sideswiped by a car is something we all want to avoid just the same. As such, it is far better to stay away from dangerous roads in the first place than to make the mistake of turning onto one.

Researchers at the University of Washington have firsthand experience with the dangers of biking on city streets. Using that experience, they have developed a technological solution that could help to avoid collisions before they have a chance to occur. Called ProxiCycle, their handlebar-mounted device monitors nearby cars and logs when they get too close. The locations of these close calls can be analyzed over time, giving cyclists a clear picture of dangerous places that would be best to avoid altogether.

The system consists of a compact sensor unit built into a 3D-printed casing that fits into the end of a bicycle’s handlebar. To sense nearby cars, a pair of VL53L8 proximity sensors were included. A Seeed Studio Xiao nRF52840 development board manages the data collection and wirelessly transmits it via Bluetooth Low Energy to a paired smartphone. Power is supplied by a small rechargeable lithium-polymer battery housed inside the handlebar. This entire setup can be assembled for under $25 using commercially available components.

During a two-month trial in Seattle, the team equipped 15 experienced cyclists with the sensor system. Over 240 rides, they logged more than 2,000 close passes. By mapping these events, the researchers were able to identify patterns and hotspots of risky driving behavior. What’s more, these locations strongly correlated with both past accident data and cyclists’ own ratings of perceived safety.

With enough user participation, the system could feed into apps like Google Maps or Strava to suggest safer routes for cyclists in real time. That could make cycling more appealing to a broader range of people — especially those who are currently deterred by safety concerns.

Cycling offers significant health and environmental benefits, yet it remains underutilized, particularly in the United States. A major reason is the fear of being hit by a car. ProxiCycle offers a scalable, low-cost way to gather safety data, helping riders steer clear of danger and ease their minds.

As urban planners continue to expand bike infrastructure, tools like ProxiCycle may offer a bridge solution, empowering riders with information until cities can catch up with safer street design. It could be a step toward not just more cycling, but smarter and safer cycling for everyone.