Headlights
A headlamp is a lamp also called
auto parts, usually
attached to the front of a vehicle such as a car, with the purpose of
illuminating the road ahead during periods of low visibility, such as
night or precipitation.
While it is common for the term headlight to be
used interchangeably in informal discussion, headlamp is the technically
correct term for the device itself, while headlight properly refers to
the beam of light produced and distributed by the device.A headlamp can also be mounted on a bicycle (with a battery or small
electrical generator), and most other vehicles from airplanes to trains
tend to have headlamps of their own.
Regulations and requirements
Modern headlamp is electrically operated, positioned in pairs, one
or two on each side of the front of a vehicle. A headlamp system is
required to produce a low and a high beam, which may be achieved either
by an individual lamp for each function or by a single multifunction
lamp.
High beams cast most of their light straight ahead, maximizing
seeing distance, but producing too much glare for safe use when other
vehicles are present on the road. Reason there is no especial control
of upward light, high beams also causes back dazzle from fog, rain and
snow due to the retro reflection of the water droplets.
Low beams have
stricter control of upward light, and direct most of their light
downward and either rightward (in right-traffic countries) or leftward
(in left-traffic countries), to provide safe forward visibility without
excessive glare or backdazzle.
Functions
High beam
High beam (main beam, driving beam, full beam) headlamps which
provide a bright, centre-weighted distribution of light with no
particular control of light directed towards other road users' eyes. As
such, they are only suitable for use when alone on the road, as the
glare they produce will dazzle other drivers. International ECE
Regulations permit higher-intensity high-beam headlamps than are allowed
under North American regulations.
Low beam
Low beam (dipped beam, passing beam) headlamps provide a
distribution of light designed to provide adequate forward and lateral
illumination with limits on light directed towards the eyes of other
road users, to control glare. This beam is intended for use whenever
other vehicles are present ahead.
The international ECE Regulations for
filament headlamps and for high-intensity discharge headlamps specify a
beam with a sharp, asymmetric cutoff preventing significant amounts of
light from being cast into the eyes of drivers of preceding or oncoming
cars.
