Editing Headlamp (section)

=== Directional headlamps ===
{{more citations needed section|date=May 2011}}
[[File:1928Willys-Knight70A.jpg|thumb|Directional (steering) headlamp (middle) on a 1928 Willys-Knight 70A Touring]]
[[File:Draaiende koplamp.jpg|thumb|upright|Directional (steering) headlamps on a [[Citroën DS]] – the driver can see clearly through curves.]]
These provide improved lighting for cornering. Some automobiles have their headlamps connected to the [[steering]] mechanism so the lights will follow the movement of the front wheels. Czechoslovak [[Tatra (company)|Tatra]] was an early implementer of such a technique, producing in the 1930s a vehicle with a central directional headlamp. The American [[1948 Tucker Sedan]] was likewise equipped with a third central headlamp connected mechanically to the steering system.

The 1967 French [[Citroën DS]] and 1970 [[Citroën SM]] were equipped<ref name="dsgoddess.com">{{cite web|url=http://www.dsgoddess.com/specs/first-directional-headlights/ |title=Myth or fact: The Citroën DS pioneered directional headlights |access-date=2009-11-29 |work=dsgoddess.com |url-status=dead |archive-url=https://web.archive.org/web/20120301105338/http://www.dsgoddess.com/specs/first-directional-headlights/ |archive-date=1 March 2012 }}</ref> with an elaborate dynamic headlamp positioning system that adjusted the inboard headlamps' horizontal and vertical position in response to inputs from the vehicle's steering and suspension systems.

At that time [[Federal Motor Vehicle Safety Standard 108|US regulations]] required this system to be removed from those models sold in the U.S.<ref>{{cite web |url=http://vintagecars.about.com/od/historygreatmoments/a/citroen_ds.htm |title=Citroën DS, a Classic Car 20 Years Ahead of its Time |website=vintagecars.about.com |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20070104231250/http://vintagecars.about.com/od/historygreatmoments/a/citroen_ds.htm |archive-date=4 January 2007 |url-status=dead}}</ref>{{failed verification|date=October 2021}}

The D series cars equipped with the system used cables connecting the long-range headlamps to a lever on the steering relay while the inner long-range headlamps on the SM used a sealed hydraulic system using a glycerin-based fluid instead of mechanical cables.{{Citation needed|date=September 2013}} Both these systems were of the same design as their respective cars' headlamp leveling systems. The cables of the D system tended to rust in the cable sheaths while the SM system gradually leaked fluid, causing the long-range lamps to turn inward, looking "cross-eyed." A manual adjustment was provided but once it was to the end of its travel the system required refilling with fluid or replacement of the tubes and dashpots.{{Citation needed|date=May 2011}}

[[Citroën SM]] non-US market vehicles were equipped with heating of the headlamp cover glasses, this heat supplied by ducts carrying warm air from the radiator exhaust to the space between the headlamp lenses and the cover glasses.{{Citation needed|date=September 2013}} This provided demisting/defogging of the entire interior of the cover glasses, keeping the glass clear of mist/fog over the entire surface. The glasses have thin stripes on their surfaces that are heated by the headlight beams; however, the ducted warm air provides demisting when the headlamps are not turned on. The glasses' stripes on both D and SM cars appear similar to rear windshield glass electric defogger heating strips, but they are passive, not electrified.{{Citation needed|date=September 2013}}