Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-08-18

! proaches from the same street he ex-
| poets to get the same treatment. The
possibilities are, however, that he won't.
The control has taken into considera-
ton the fact that Smother vehicle Is
approaching along the main thorough
| fare and since It believes in the cour-
tesy rule Of FIRST come first served" 1t
keeps him waiting until this car has
passed the intersection.
Then comes another surprise. The
control apparently knows" when the
Immediately signals the cross street
traffic to PROCEED. About this time II
begins to dawn on the latter that
somewhere, somehow a super-intelli-
! gence is at work on the intersection.
and he may go home and refresh his
mind on the fundamental principles OF
engineering to find clue to the niys-
terry.
The explanation to the foregoing sit
uation Is very simple The control
knew" when the thoroughfare driver
approached the intersection because II
saw" 1t through one Of its sensitive
units It reasoned that the thor
oughfare driver, when the light favored
him. would cross in a certain number
Of seconds, and allowed him that time.
The time allotted for crossing varies
with the speed Of the vehicle.
Driver Must BE Alert.
If the driver had not taken advan-
tage Of the opportunity offered he would
have lost the chance. The control
would have reversed the orders TO the
lights and allowed the cross street
vehicle to pass.
When the motorist gets this far In
his understanding of the mechanism he
| often attempts to create situations that
will stump the control. It Is plain to
see how It functions under simple con-
ditions involving only two cars. But
what occurs, he asks, under complex
situations involving a number OF We
hicles.
If the mechanical policeman does
its work as thoroughly as . human
policeman, he reasons, 1t should favor
thoroughfare traffic, but to. do this
J 1t must use a certain amount OF Juog-
ment. How, he inquiries. can an as
sortment of wires and impulses use
Judgment!
Here the robots calculations are based
on the normal behavior of traf1c. 1t
does favor tforoughfare trafic, but,
like the human policeman. 1t gives cross
street traffic fair break. There are
always occasional breaks in a steady
| line Of cars, and the control gives cross
street cars the beneflt Of them. Cars
| approaching an intersection when there
is no opposing trafic are given the
green light instantly.
But suppose there Is no break for
long time, asks the motorist. Sup.
pose there is steady flow Of trafac
on the thoroughfare. No car Is re-
quired to wait for more than o set
maximum period Of time against OPP
posing traffic; this period is very hex-
ible and is adjustable at the discre-
ton of the traf1c authorities.
The "electromatic" control Is so
flexible that If a gap comes In o stream
of trafic, before the maximum period
Of time has been reached, and there
are cars waiting on the opposing street.
the control will take advantage Of the
break instantly. and give . green
light to the waiting cars, automatically
returning to the busy street upon cessa-
ton Of trafic on the cross streets.
Actually, the trafic lights give the
signal, as these are the only means
by which the mechanism can express
itself. But there are thinking" and
reasoning" behind the signals, and
judgment Of a purely mechanical ma
ture which admits Of no faults. II
there are no cross street cars and
the intersection is a busy one. there
are bound to be pedestrians waiting.
The control has not forgotten the pc
destrians and allots q certain number
of seconds for them to get across the
thoroughfare.
! Pedestrians move with the trafic as
| they do with o policeman or any other
type of signal system. They have the
same opportunity as the cars going in
trafic or watch the lights, as they
prefer.
But the motorist who thinks there
IL sorne way In which the control can
be outwitted is still not satisfied. He
wants to know what the lights viii do
when there is no trafic on either thor
oughfare or cross street. His thought
is that If there are no vehicles APP
preaching, the control must be blind
and dormant.
Remembers Pedestrian.
But again he is wrong. The control
mechanism Is still busy with its
Thoughts" "If there is q car beyond
the range of my eyes" it says to it.
self, "tiie chances are nine to one It
will approach on the thoroughfare. I
viii give the thoroughfare the green
light but II q cross street car APP
proaches and the thoroughfare Is clear,
| / will switch over and let him through.
But must remember the pedestrians
on the cross street, however. and II
both streets continue clear indefinitely
| VIII switch the Slgnal lgHCS every SV
seconds to let the pedestrians over"
Under ordinary conditions a car APP
preaching an intersection can do one
of three things: Turn right, left. or go
straight. The control is not interested
in knowing which of these three
courses will take certain number OF
seconds and 1t gives the driver this
opportunity to proceed on his way. !.
Continuous trafic on State arterial
highway is never interrupted unless
vehicles or pedestrians actually wish
to cross the artery, and even then the
arterial highway trafic is held up Tor
Just q suficient length Of time to allow
whatever opposing trafic there may De
to cross its path.
| A feature of the electro-matic ap-
paratuS is the fact that 1t may be adj
justed to suit conditions at any speci-
fed intersection. The pauses between
signals or their duration can be varied
at will. On wide thoroughfares with
room for several trafflc lanes additional
apparatus may be installed which VIII
direct drivers desiring to make either
Q right or left turn.
i Trolley cars can be connected with
i the control as well as automobiles. but