The lights have become smaller over time and “any given intensity appears brighter when emitted from a smaller visible surface than a larger one,” said Daniel Stern, editor-in-chief of Driving Vision News, a magazine covering the automotive lighting industry.
“Big pickups and SUVs and short, small cars are popular at the same time,” he added. “The eyes in the low car are hit hard every time by the lights mounted high on the SUV or truck.” (Almost half of the 280 million registered cars in the US are SUVs or pickups.)
LED and headlights with high intensity discharge can appear bluer than halogens in their power spectrum, and they often cause “significantly stronger reactions to malaise” than warm white or yellowish lights, said Stern.
“Blue light is difficult for the human visual system to process because blue wavelengths tend to focus right in front of the retina, not on it,” he said.
Mark Baker, founder of an activist group called Softlights, said that while the blue LEDs might be some of the best for night driving, that didn’t mean they’re good for everyone.
“It is true that blue allows you to keep shining,” he said. “When you say, ‘I’m making the biggest and worst light that I can,’ don’t pay attention to the receptors of another driver walking towards you.”
“Brightness” is not a commonly accepted term by scientists and researchers that instead refers to lumens or the power of a light. Halogen lamps deliver 1,000 to 1,500 lumens, while high pressure discharge lamps and LEDs can measure 3,000 to 4,000 lumens.