I remember my driver's ed teacher, circa ~2003, teaching us that if the oncoming car has its high beams on, you can look at the white line on the right side of the road and it'll keep you in your lane without getting too dazzled. Didn't really need it much then, but it's become more and more essential over the years. Now sometimes I flash the oncoming driver because I think they've got their high beams on, only to get an absolutely eye-searing flash in return -- they just had over-bright headlights!
Do newer LED headlights even have a duty cycle?