Editing Headlamp (section)

==== Advantages ====

===== Increased safety =====
Automotive HID lamps offer about 3000 [[lumen (unit)|lumen]]s and 90 [[Candela|Mcd]]/m<sup>2</sup> versus 1400 lumens and 30 Mcd/m<sup>2</sup>{{disputed inline|date=November 2012}} offered by halogen lamps. In a headlamp optic designed for use with an HID lamp, it produces more usable light. Studies have demonstrated drivers react faster and more accurately to roadway obstacles with good HID headlamps compared to halogen ones.<ref>{{cite web|url= http://www.lrc.rpi.edu/programs/transportation/pdf/PAL/PAL2001-vanderlofske.pdf |title=Evaluation of High Intensity Discharge Automotive Forward Lighting |access-date=2010-12-29}}</ref> Hence, good HID headlamps contribute to driving safety.<ref>{{cite web|url= http://www.drivingvisionnews.com/index.php?option=com_content&view=article&id=index.php?option=com_content&view=article&id=947 |title=VISION Congress report |website=Drivingvisionnews.com |date=2008-09-02 |access-date=2010-12-29}}</ref> The contrary argument is that glare from HID headlamps can reduce traffic safety by interfering with other drivers' vision.

===== Efficacy and output =====
[[Luminous efficacy]] is the measure of how much light is produced versus how much energy is consumed. HID lamps give higher efficacy than halogen lamps. The highest-intensity halogen lamps, H9 and HIR1, produce 2100 to 2530 lumens from approximately 70 watts at 13.2 volts. A D2S HID bulb produces 3200 lumens from approximately 42 watts during stable operation.<ref name=R37/> The reduced power consumption means less fuel consumption, with resultant less {{CO2}} emission per vehicle fitted with HID lighting (1.3 g/km assuming that 30% of an engine running time is with the lights on).

===== Longevity =====
The average service life of an HID bulb is 2000 hours, compared to between 450 and 1000 hours for a halogen lamp.<ref>{{cite web |url=http://www.friarsmarketing.com/Resources/Lighting%20Programme%20Autom%2367.pdf |title=Osram Automotive Lamps Lighting Programme 2005–06 |website=Friarsmarketing.com |access-date=2010-12-29 |url-status=dead |archive-url= https://web.archive.org/web/20080612073847/http://www.friarsmarketing.com/Resources/Lighting%20Programme%20Autom |archive-date=12 June 2008}}</ref>