Don't take this the wrong way; that bike helmet is certainly an important piece of safety equipment, and it can save your life in a crash. However, one report showed that it can also elevate the chances of that crash happening in the first place.
A researcher, in talking with friends of his who rode their bikes often, heard them mention that having a helmet on seemed to decrease the distance between them and passing cars. In other words, drivers who saw them riding with a helmet didn't feel the need to give them as wide of a berth.
The researcher was rather perplexed and decided to test the theory for himself. He rode his bike around, complete with ultrasonic sensors, as a total of 2,300 vehicles passed him. Sometimes he wore a helmet, and other times he did not.
Twice, he made light contact with other vehicles. Once it was a bus, and the other time it was a truck. In both cases, he was wearing a helmet.
When he looked back at the data, he found that drivers got 3.35 inches closer to him, on average, when he had his helmet on. They gave him slightly more room with a bare head.
He also tested out wearing a wig, making it look as if he were a female cyclist to drivers who came up behind him to pass. He found that drivers gave men less room than women, by an average of 2.2 inches.
This is slightly troubling research. Cyclists can still be badly injured even with helmets on, but it seems that drivers are willing to take more risks. Those who get hurt in resulting accidents must know their rights.
Source: Scientific American, "Strange but True: Helmets Attract Cars to Cyclists," Nikhil Swaminathan, accessed Feb. 23, 2018