Evening star., 1934-07-22

top of a hill simultaneously a car
approaching from the other side
reaches almost the same spot. Its
- headlights blind the other driver who,
maintaining his rapid pace, fails to follow the
exact contours of the road, loses control and
crashes into telephone pole.
This dangerous plight of the night motorlSt
is now in a fair way of being solved, thanks
to Government scientists here in Washington.
In fact virtually every phantom of the night
that botherS the driver after dark has been
investigated painstakingy by automotive ex-
perts of the Bureau of Standards and Public
Roads in the most thorough study of the kind
ever made. All motorists will be interested TO
note the results, many of them surprising, to
say the least
Stop that terrible night driving glarel This
was the first objective of the Federal research
specialists, and in this connection they utilized
many novel instruments and gadgets devised
especially for the tests, besides almost thou
sand feet of motion picture film. Test cars,
equipped with four different types of head
lights at a time, were driven at all speeds
around dangerous curves, along rough country
roads. smooth State highways indeed. under
every conceivable condition confronting the
average motorist at night.
One unique device used is the "potenti-
ometer," which accurately measures how much
current is flowing through the headlamp and
therefore is able to maintain the lights at a
constant strength. This is small instrument,
easily connected with the cars battery.
A MOTHER instrument is the "stadi-
meter" also known as the automatic
tape line" because it is about 10 times as fast
as the ordinary tape line in making important
measurements of just how far away one car
is from test auto while making headlamp
experiments. This Is an optical type of device
nSPd to sight another while held in the
hand very much in the fashion of a sur
veyor's sighting rod.
Every motorist will be glad to know that the
test program revealed that practically all the
headlamps fitted on American cars during the
past three years are capable of furnishing ade-
quate and safe road lighting However a single
driving beam on your headlight is not enough
the experts proved. For there are many occa-
sions when the high-intensity part of the beam
viii strike the oncoming drivers eye. This is
due to bouncing of the rough roads
DETECTION when loaded with passengers and
passing over slight rises.
Consequently, all modern headlampS, and
about go per cent of those on the roads today
provide dual-purpose lighting consisting of an
upper beam for good road lighting at touring
speeds and lower beam for safety and COM
fort in passing. This important feature is ac-
compshed through the use of a lamp having
two flaments. BY the simple flick of a switch
usually located the steering column be-
meath the foot the driver instantly can shift
from the beam which lights UP the road sew
eral hundred feet in advance of the car to the
depressed" beam which is down. well out OF
the other fellows eyes And this depressed
team provides Illumination of high intensity
on the road close to the car and at the sides
of the road. giving positive indication of the
pavement edge regardless of how glaring are
the passing drivers lights.
In other words, most modern headlamps. the
Government specialists found considerably tC
their own surprise are capable of producing
excellent lighting without Objectionable glare
But they must be in proper focus and cor
rectly aimed. If the f1lamentS are either ahead
behind the focal point of the reflector, less
relief will be obtained by fitting the driving
beam. Where this situation exists, much OF
the light that ordinarily would be directed or
the road will be shot up III the air and con-
sequently wasted. After the headlamps have
been properly focused, they must be pointed
straight ahead and adjusted so that the tor
Of the driving beam is slightly below the hori-
Eontal, to conform with most State regula-
tions Practically all the States require that
with the car loaded. on level ground. 25 feet
away from vertical surface. the top of the
beam should be Just below the height of the
headlamp centers.
lNCLE SANS experts point out that tht
~ driver. from his own experience, can de-
termine when it is necessary to depreSs or lower
his main beam. The distance depends ON road
conditions weather and speed On level road:
the beam should be dropped when the car is
about 500 feet from the passing motorist oi
sooner If the oncoming driver signals for re-
hef The beam should always be depressed
when passing over the top of rise. and de-
pressed earlier when the road is excessively