....complaints about glare have increased considerably within the past 25 years, most of them due to the new light source technology itself.
....photometric standards have not evolved with changes in the spectral power distribution of LED technology.
....The light emitted by LEDs has become bluer, brighter, sharper, and more focused — all of which help a driver see better at night. A bluer LED light in fact is brighter to the human eye than the same measured level of yellower light emitted by halogen headlights. In effect, the conventional photometry underlying all lighting standards simply does not capture this enhanced LED brightness, which, in fact, also increases real glare from oncoming headlights.
....Exacerbating the photometric insensitivity to brightness and glare in standards, most state governments no longer require drivers to have properly aimed headlights. A recent study from the Light and Health Research Center laboratory found that nearly two-thirds of licensed automobiles had one or both headlights misaimed. With a greater proportion of sport-utility vehicles and pickup trucks with high-mounted headlights on the road, those misaimed and highly focused headlights are even more likely to direct greater amounts of light into drivers’ eyes.