ARE BLUE HEADLAMP BULBS DANGEROUS?
Yes, they are. Here are the nuts and bolts of why blue bulbs are a bad idea: The output spectrum of halogen headlamp bulbs includes *very* little light in the blue frequency range. These blue bulbs have a filter coating on them that allows only the blue frequencies through the filter. Because very little light is produced by a halogen bulb in this range in the first place, it is only this very small amount–a tiny fraction of the total amount of light produced by a halogen bulb filament–that ever reaches the road. This can be confirmed this with a good-quality non-chromosensitive light meter; even a very apparently-bright blue bulb actually throws very little light. Recent tests by the US Department of Transportation’s Office of Crash Avoidance Standards found that a standard-wattage 9004-type blue headlamp bulb reduced the road lighting ability of a standard headlamp by 67%, and increased glare for oncoming and preceeding trafic by 33%. This illustrates the difference between the sig
