Main Light Sources for Headlights

Xenon - HID
· “Projector-style HID headlamps may be contributing to discomfort glare because their surface area is smaller than standard headlamps and so their luminance is much higher.”
http://www.aaafoundation.org/pdf/HeadlightGlare.pdf

· “HID headlamps typically have two to three times the light flux (volume) of halogen lights, but because the HID filament is smaller, they allow the light to be controlled more precisely.”
http://www.aaafoundation.org/pdf/HeadlightGlare.pdf

· “Properly aimed, and when not flashing, these HID lamps may not appear significantly brighter than halogen sources if their size is relatively the same. However, if misaimed, and when flashing, these lamps will appear brighter and will produce significantly more glare than a normal halogen lamp.”
http://www.aaafoundation.org/pdf/HeadlightGlare.pdf

· HID headlamps are more efficient than halogen headlamps and you can produce more light with a smaller headlamp; however, if you have too much then the contrast between the roadway directly in front of you and the area in your peripheral vision will be increased and potential for glare will increase
http://www.danielsternlighting.com/tech/bulbs/Hid/disadvantages/disadvantages.html

· Estimated to last the life of the vehicle (10 years, 160,394.4 km (100,000 mi)) under normal operating conditions – much longer than halogen lamp life
http://www.tfhrc.gov/safety/hsis/pubs/04146/introduction.htm

· Better performance and efficiency - “The luminous efficacy, which is the ratio of luminous output to electrical power consumption, is much greater in discharge lamps compared to halogen designs. Various lighting manufacturers claim that discharge lamps have at least twice the lumen output as halogen lamps with comparable wattage.”
http://www.tfhrc.gov/safety/hsis/pubs/04146/introduction.htm


Halogen
· Human eye’s color perception and differentiation is better under halogen light than under HID automotive headlamps
http://www.danielsternlighting.com/tech/bulbs/blue/bad/bad.html

· “light output of just over 1,000 lumens (lm) while operating at 12.8 volts (V)”; “average luminance of halogen bulbs can be around 1,400 candela per square meter (cd/m²) (408 footlamberts (fL)”
http://www.tfhrc.gov/safety/hsis/pubs/04146/introduction.htm

· disadvantage of halogen lamps is that “roughly 80 percent of the output is lost as heat in the infrared spectrum. In addition, the filaments in halogen systems can be damaged from road vibrations and other effects associated with long-term use. As a result, halogen headlamps may not last as long as other components in the vehicle.”
http://www.tfhrc.gov/safety/hsis/pubs/04146/introduction.htm