Prompt Critical Posted: Well, most of the threats come from the rear, so now that I have a radar unit, I've been pondering some sort of interface with a device aimed at the windshield of the driver's car. Any suggested devices? Oh, must be legal in California, so that leaves out many of the more interesting ideas.
I read a study from some years ago and the study said that 89% of car bicycle collisions happened at intersections. Although the study was done decades ago, Intersections are still a major danger even with considering modern electronic distraction. Noise, bright lights and quick movement attract the attention of others. In heavy traffic a very loud whistle, horn and a flashing amber daylight visible light would help. I have always just yelled with very good results, most of the time.