THE
AMERICAN EXPERIENCE AS STATED BY NHTSA
Extracts from
the reports:
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 01-8885; Notice 01]
RIN 2127-AH81
Glare from Headlamps and other Front Mounted Lamps
Federal Motor Vehicle Safety Standard No. 108;
Lamps, Reflective Devices, and Associated Equipment
1. Background
At the turn of the Twentieth century,
with the automobile industry still in its infancy, some
vehicles began to be equipped with kerosene lamps for use as
night time road illumination. Within ten years, vehicle
manufacturers began to use electric headlamps on vehicles.
In 1914, members of the Society of Automotive Engineers (SAE)
who were involved in the design and specification of motor
vehicle lighting began to express their first concerns about
the glare produced by these headlamps. Since that time, SAE
members, who were primarily lighting and optical engineers,
and human factors scientists have sought various ways to
reduce glare for other drivers and, at the same time,
improve the roadway illumination for drivers. Over the
years, hundreds of variations of headlamps and unique
technologies have been implemented on motor vehicles. For
example, there were many variants of glare reducing devices,
before lower and upper beams became the norm, that were
achieved by a mechanical metal shield that was rotated into
place in front of the bulb within the headlamp, typically by
using a driver actuated cable. The effect was to reduce the
emitted light, either direct or reflected, leaving only
light directed away from oncoming drivers. Another example
from about 1929, was General Electric's Tung-Sol Blue-Wite
TM headlamp bulb. It was advertised as providing whiter
light for safer road illumination and added comfort, with
courtesy extended to others. The pale blue color of the
glass, reduced the red content of the light emitted. It was
claimed to be the latest development at the time.
Many reams of paper in the form of formal
research reports, technical papers and meeting minutes of
the World's motor vehicle lighting experts have been
generated over the last nine decades to discuss and tune the
delicate balance between glare and vision at night from
motor vehicle headlamps. These resulted in fairly consistent
decisions among the headlamp researchers and designers
around the world. The resultant beam pattern specifications,
with some subtle variations to accommodate specific roadway
and driving conditions in different countries, have been
incorporated in the lighting regulations of many countries
for many decades.
The balance the agency has maintained
between visibility for the vehicle operator while minimizing
glare for other operators has changed very little since its
federal codification. In 1968, however, light trucks
represented only 10 percent of light vehicle sales and the
most advanced technology used then for lighting was
incandescent filament type sealed beam lamps.
The allowable range of total illumination
performance is fairly wide. There are points in the beam
that require minimum levels of intensity, maximum levels and
some that have both minimums and maximums. Between those
points, there are no requirements. The NHTSA assumption has
been that the nature of headlamp optics tend to make
additional test points not necessary.
The nature and response to glare is
interesting. Whether from headlamps or lamps in your home,
there is a distinction between glare that is disturbing and
glare which is disabling. Essentially, as the intensity of a
light source increases, the impression of the light seen by
observers can range from barely noticeable to disturbing,
and eventually disabling. The particular response of an
individual to any glare source varies based on its
luminance, the intensity of ambient lighting, the distance
and angle between the light source and the observer, the
duration of observation, the age of the observer, and many
other factors. Controlling the intensity of the light source
is one variable among many dozens that affect the glare for
drivers. Controlling the location of the light source,
relative to the observer's line of sight, whether direct
view or indirect view (e.g. from mirrors) is another way.
Quote from the same report:
QUOTE
Some lighting
researchers have suggested that net visibility would be
maximized if all drivers would use only upper beams. While
this may sound incredible, it is based on findings that the
increase in roadway illumination would provide greater
benefit than the high glare from upper beams would take
away. While this is an interesting observation, the driving
experience at night would not be optimized, based on the
volume of complaints of glare with current headlamps. This
raises the issue of whether NHTSA's balance between glare
and roadway illumination should move toward less glare even
if that means less visibility of the roadway environment.
UNQUOTE
All the above point
to the fact that dipping is a solution and if manual dipping
is not dependable then auto dipping is the best solution.
