Editing Headlamp (section)

=== {{Anchor|Headlamp leveling|Headlamp leveling systems}} Headlamp leveling systems ===
[[File:Leuchtweitenregulierung.svg|thumb|200px|Headlamp leveling]]
The 1948 [[Citroën 2CV]] was launched in France with a manual headlamp leveling system, controlled by the driver with a knob through a mechanical rod linkage. This allowed the driver to adjust the vertical aim of the headlamps to compensate for the passenger and cargo load in the vehicle. In 1954, [[Cibié]] introduced an automatic headlamp leveling system linked to the vehicle's suspension system to keep the headlamps correctly aimed regardless of vehicle load, without driver intervention. The first vehicle to be so equipped was the [[Panhard Dyna Z]]. Beginning in the 1970s, Germany and some other European countries began requiring remote-control headlamp leveling systems that permit the driver to lower the lamps' aim by means of a dashboard control lever or knob if the rear of the vehicle is weighted down with passengers or cargo, which would tend to raise the lamps' aim angle and create glare. Such systems typically use [[stepper motor]]s at the headlamp and a rotary switch on the dash marked "0", "1", "2", "3" for different beam heights, "0" being the "normal" (and highest) position for when the car is lightly loaded.

Internationalized [[World Forum for Harmonization of Vehicle Regulations|ECE Regulation]] 48, in force in most of the world outside North America, currently specifies a limited range within which the vertical aim of the headlamps must be maintained under various vehicle load conditions; if the vehicle isn't equipped with an adaptive suspension sufficient to keep the headlamps aimed correctly regardless of load, a headlamp leveling system is required.<ref name="R48">{{cite web|url= http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/updates/R048r12e.pdf |title=ECE R48 }}&nbsp;{{small|(649&nbsp;KB)}}</ref> The regulation stipulates a more stringent version of this anti-glare measure if the vehicle has headlamps with low beam light source(s) that produce more than 2,000 lumens – xenon bulbs and certain high-power halogens, for example. Such vehicles must be equipped with headlamp self-leveling systems that sense the vehicle's degree of squat due to cargo load and road inclination, and automatically adjust the headlamps' vertical aim to keep the beam correctly oriented without any action required by the driver.<ref name=R48/>

Leveling systems are not required by the North American regulations. A 2007 study, however, suggests automatic levelers on all headlamps, not just those with high-power light sources, would give drivers substantial safety benefits of better seeing and less glare.<ref>{{cite journal|title=Benefits of Headlamp Leveling and Cleaning for Current U.S. Low Beams|journal=UMTRI|date=November 2007|first1=Michael J.|last1=Flannagan |first2=Michael |last2=Sivak |first3=Brandon |last3=Schoettle |url= http://deepblue.lib.umich.edu/bitstream/2027.42/58733/1/100247.pdf|access-date=2010-04-25 }}</ref>