Another result of the new look in lighting was a prolonged debate and series of studies regarding the glare effects of xenon headlamps vs. tungsten-halogen ones: Were the complaints of increased glare substantive? Or were the new lights just drawing complaints because their different appearance attracted inadvertent attention?
Two reputable American research groups reached opposite conclusions:
– One group of scientists at a well-respected Midwestern traffic research institute found the bluer light from xenon headlamps is almost 50% more glaring than tungsten-halogen light of the same intensity, with no concomitant seeing benefit.
– But another group of lighting researchers affiliated with a long-established East Coast technical university, in carrying out a study sponsored by a maker of blue-tinted bulbs, found a significant seeing benefit to the blue bulbs, with no significant increase in glare.
Both research centres’ subsequent studies have referenced and reinforced these respective results.
While some regulatory parties have never been especially happy with the blue-white colour of HID headlamps, the world’s marketers have used this appearance as a selling point, and it is now visually de rigueur on luxury cars.
The debate is now heating up again, as the emergence of LED headlamps opens up options for an unprecedented range of white colours from less than 3000K to more than 5500K. Do drivers’ subjective preferences correlate positively or negatively with seeing? With glare? What’s the optimal colour for headlamp performance? For glare avoidance? And might there be a benefit to changing light colour, not just beam distribution, as part of an advanced AFS?
Further research is warranted!