Headlamps and other lighting equipment

Most low-beam headlamps are specifically designed for use on one side of the road or the other. Headlamps for use in LH-traffic countries have low-beam headlamps that "dip to the left", i.e., the light is distributed with a downward/leftward bias to show the driver the road and signs ahead without blinding oncoming traffic. Headlamps for RH-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 RH-traffic headlamps in a LH-traffic country or vice versa for a limited time (as for example on holiday or in transit), it is a legal requirement to adjust the headlamps temporarily so that the wrong-side hot spot of the beam does not dazzle oncoming drivers. This may be achieved by adhering blackout strips or plastic prismatic lenses to a designated part of the lens, but some varieties of the projector-type headlamp can be made to produce a proper LH- or RH-traffic beam by shifting a lever or other movable element in or on the lamp assembly.

Because blackout strips and adhesive prismatic lenses reduce the safety performance of the headlamps, most 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. In the UK, US government and military personnel who brought RHT/LHD cars with them used to 'trade' headlamp assemblies with a person returning to the US^{[citation needed]}. The newcomer then had proper LHT lights and the US-bound returnee had proper RHT ones again. As most 50s-80s headlamps were interchangeable, this 'swap' could save motorists time and money.

Anecdotal reporters have observed the requirement to adjust headlamps for the traffic-handedness of the country is increasingly flouted, and is now rarely enforced by European police forces. In France, this may be due in part to the 1993 deletion of the previous requirement for Selective yellow headlamp light; foreign-registered vehicles are now much less conspicuous at night.

Without sidecars attached, motorcycles, motor scooters, mopeds, and bicycles are almost symmetric with their handlebars in the centre. However, motorcycles are often equipped with automotive-type asymmetrical-beam headlamps that likewise require adjustments or replacement when brought into a country with opposite traffic-handedness.