[helsinkiandrew]

This sounds like a great idea in theory but in practice my guess is that its too little (this won't help cars pulling out of junctions into bikes and many other dangerous scenarios) and too late (how much time will the driver have to see the strobe/hear the horn and take evasive action).

The Radar powered Garmin Varia (https://buy.garmin.com/en-GB/GB/p/601468) is probably simpler and cheaper and I'd guess more likely to work reliably in bad lighting conditions.

But a good set of continuously flashing ultra bright strobe lights, high visibility/reflective clothing, and bike lanes or driver education is by far superior.

[Luxonis-Brandon]

Thanks for the comments! So the radar solution is great for touring riders, where one doesn't see a car for half an hour or a couple hours. It mentally wakes them up to the presence of a car.

It's not intended for use in commuting though... as in commuting you don't care about the 500 cars that will pass you safely on your ride (and you don't want 500 alerts), you care about the 1 that is on a trajectory to kill you.

So with computer vision you can tell that trajectory. You can also with radar, but only with super-expensive radars ($100k+), wheras you can do this w/ computer vision for $50 or so.