I used to wear a helmet while commuting in the DC area. I think I was the only one. I do wonder whether it might increase my risk of neck injury, because it's difficult to find a helmet that doesn't push your head too far forward, especially with the new car seat designs that all put the whiplash backrest too far forward for comfort.
In a small town, it's more of an issue, because people will recognize you. But on the beltway of a major city, who cares? If they think I'm crazy, they'll just give me more space.
I stopped because I decided it was more important to wear a painter's respirator when driving on the DC beltway. This greatly reduced the number of headaches I got while driving. It's a little awkward to wear both.
Interesting. I tried a dust mask before when riding my bike because I was annoyed by breathing car exhaust. I should not have been surprised by how much harder it made breathing in general in retrospect. Perhaps a mask with minimal filtering would be okay, but anything more makes breathing very difficult. Such masks are not designed for when you need more oxygen than normal, and such a mask might not even be possible. You might need something like a SCBA.
A 2006 study showed that “280,000 people in the U.S. receive a motor vehicle induced traumatic brain injury every year” so you would think that wearing a helmet while driving would be commonplace. Race car drivers wear helmets. But since almost no one wears a helmet while driving a regular car, you probably fear that if you wore one you would look silly, attract the notice of the police for driving while weird, or the attention of another driver who took your safety attire as a challenge. (Car drivers are more likely to hit bicyclists who wear helmets.)
The $30+shipping Crasche hat is designed for people who should wear a helmet but don’t. It looks like a ski cap, but contains concealed lightweight protective material. People who have signed up for cryonics, such as myself, would get an especially high expected benefit from using a driving helmet because we very much want our brains to “survive” even a “fatal” crash. I have been using a Crasche hat for about a week.