Editing Headlamp (section)

=== Compatibility with traffic directionality ===
{{see also|Right- and left-hand traffic}}
[[File:Dagen H Headlamp.jpg|thumb|right|200px|Headlamp sold in Sweden not long before [[Dagen H]] changeover from left to right hand traffic. Opaque decal blocks the lens portion for low beam upkick to the right, and bears the warning: "Not to be removed before 3 September 1967".]]

Most low-beam headlamps are specifically designed for use on [[Traffic directionality|only one side of the road]]. Headlamps for use in left-traffic countries have low-beam headlamps that "dip to the left"; the light is distributed with a downward/leftward bias to show the driver the road and signs ahead without blinding oncoming traffic. Headlamps for right-traffic countries have low beams that "dip to the right", with most of their light directed downward/rightward.

Within Europe, when driving a vehicle with right-traffic headlamps in a left-traffic country or vice versa for a limited time (as for example on vacation or in transit), it is a legal requirement to adjust the headlamps temporarily so that their wrong-side beam distribution does not dazzle oncoming drivers. This may be achieved by methods including adhering opaque decals or prismatic lenses to a designated part of the lens. Some projector-type headlamps can be made to produce a proper left- or right-traffic beam by shifting a lever or other movable element in or on the lamp assembly.<ref>{{cite web|url= http://pages.citebite.com/p4a2w8a1ojrn |title=Driving Abroad: Headlights |publisher=UK Automobile Association |date=1 August 2012 |access-date=29 May 2014}}</ref> Many tungsten (pre-halogen) European-code headlamps made in France by Cibié, Marchal, and Ducellier could be adjusted to produce either a left- or a right-traffic low beam by means of a two-position bulb holder.

Because wrong-side-of-road headlamps blind oncoming drivers and do not adequately light the driver's way, and blackout strips and adhesive prismatic lenses reduce the safety performance of the headlamps, some countries require all vehicles registered or used on a permanent or semi-permanent basis within the country to be equipped with headlamps designed for the correct traffic-handedness.<ref>{{Cite web|url=http://bfgnet.de/advice/vlo/change-to-headlights-requirements.html|title=BFG: Headlights}}</ref><ref>{{Cite web|url=http://www.arrse.co.uk/community/threads/changes-to-vehicle-headlight-policy.67707/|title=Changes to vehicle headlight policy. &#124; Army Rumour Service|date=11 September 2007 }}</ref> North American vehicle owners sometimes privately import and install [[Japanese domestic market|Japanese-market (JDM)]] headlamps on their car in the mistaken belief that the beam performance will be better, when in fact such misapplication is quite hazardous and illegal.<ref>{{cite web|url= http://www.danielsternlighting.com/tech/lights/codes/codes.html#Dip |title=Headlamp traffic-handedness |website=Danielsternlighting.com |date=2008-01-28 |access-date=2010-12-29}}</ref><ref>{{Cite web|url=http://drivesmartbc.ca/miscellaneous/right-hand-drive-vehicles-left-hand-drive-world|title=Right Hand Drive Vehicles in a Left Hand Drive World &#124; DriveSmartBC|website=drivesmartbc.ca}}</ref>