Comment by Mawr
7 hours ago
It's not a brightness thing, after all car headlights are probably 1000x brighter than anything you may have on your bike.
It's because 99% of bike lights are basically just flashlights, spraying light everywhere. The solution is the same as for cars — lights with horizontal cut-offs.
I do some optical engineering, and once took a course on lighting design. Indeed, bike lights are unregulated, and therefore, un-engineered. During the winter on my commute home from work, I usually have to cover my eyes on the bike path to avoid being blinded by oncoming cyclists.
I think Germany has regulations on this. I've bought lights on AliExpress that have a cut-off.