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THE BLOCK SYSTEM:
The appalling accident at Terra
Cotta, following so closely on the heels
of the wreck which i-esulted in the
death of President Spencer, and fol
lowed by the dreadful disaster on the
Rock Island at Topeka, Kaus., tends
to destroy our faith in the much
talked-of block system. Two at least
of these three recent conspicuous col
lisions, resulting in the aggregate in
the death of almost a hundred persons
and in the maiming of a hundred more,
occurred on roads which have been
operating for years under the block
system. This system, wnich we have
been led to believe would be the
remedy for such occurrences, appears
to have been found wanting. But
closer study of the situation will re
veal the fact that the men, not the
system, are to blame. Had the sys
tem been rigidly observed, none of
these accidents would have happened.
A chain is no stronger than its weak
est link, and man is the one weak link
in the otherwise impregnable block
system.
So long as the lives of passengers
arc in the hands of a sleepy signal
man or an overworked engineer they
are not safe. “To err is human,”
and the sad truth of this has been
brought home to us of late, as never
before.
The only solution of the problem
of the immunity from collisions ap
pears to lie in the absolute elimina
tion of the human element; in othei*
words, in the adoption of the “auto
matic stop” system. With this system
the signals are automatically set, and
a train automatically stopped, if it
attempts to run past a danger signal.
Has Proved Satisfactory.
The automatic stop system is in
use on the Boston Elevated and in
the New York Subway, and has given
entire satisfaction. Its use would
have absolutely prevented all three ac
cidents referred to above. It is rath
er expensive, it is true, but what is
S7OO a mile compared with the enor
mous loss of life and property that oc
curred at Terra Cotta? And more
over, the traveling public would prefer
to pay more money for safe transpor
tation than to risk life or limbs on a
road inadequately equipped with safe
ty devices. This, granting for the
sake of argument that the absolutely
automatic equipment would in the long
run be more expensive than the pres
ent system used by the Baltimore and
Ohio Railroad.
There are two distinct methods of
operating trains on a railroad. The
trains may be dispatched one after an
other at intervals, according to a pre
arranged schedule, allowing so many
minutes between successive trains.
This is known as the time interval
method of operation. Or the trains
may be so run that one train is al
lowed to pass a given point only when
a preceding train has passed a certain
other point a predetermined distance
in advance. This is known as the
space interval method of operation,
and roads employing this method are
said to operate under the block sys
tem The block system, then, is any
arrangement wheieby an absolute
space interval is preserved between all
moving trains. It is obvious that
where such a system is rigidly ob
served rear-end collisions are impos
sible.
A block, then, is any given length
of track into which the road is ar-
By J. HANSON BOYDEN, Late Assistant Examiner, Division of Railroads, U. S. Patent Office.
bitrarily divided, and the end of a
block is a controlling point for all
trains. The blocks may vary in length
from a few hundred feet on roads
where the traffic is congested to sev
eral miles on roads where the trains
are few.
The Telegraph Block.
The maintenance of blocks and con
sequent control of trains is carried out
in a number of different ways. One
of the earliest, and, also most com
mon of block systems, is that known
as the telegraph block. This con
sists simply in having at the ends
of each block telegraph operators
who communicate to each other advice
in regard to train movements. The
stations are provided with ordinary
semaphore signals, operated by hand,
by means of which the trains may be
controlled. Operator A, at the begin
ning of the block or section, holds
train No. 2 till advised by operator B,
at the other end, that train No. 1 has
left the blocks. This is the system in
use on the Baltimore and Ohio and
on the Southern. If properly enforc
ed and observed, it is very efficient,
but the recent accidents show how lia
ble it is to error and carelessness on
the part of employes.
Another well known system largely
in use is the controlled manual. The
organization is the same as that out
lined above, except that the various
signal levers are locked and controlled
by electric circuits which extend from
one block station to the next. Thus
a signal lever at one station, is posi
tively controlled, electro-mechanically,
by the operator of the next station in
advance, and it is, therefore, impossi
ble for the first signalman to give
a train permission to proceed, except
with the knowledge and consent of the
second signalman. This is the so
called “lock and block” system.
- A simple modification of this ar
rangement is known as the “staff sysr
tern,” which, however, is only adapt
ed for single track roads, on which
trains travel in both directions. In
carrying out this system, small metal
rods or “staffs” are provided at each
station, and held normally in a frame
by means of electric locks, controlled
from the next station. Possession of
one of these staffs by an engineer con
stitutes a permit or pass, and gives
him rhe absolute right of way over
the block.
As the locking frames are connected
electrically in pairs, and so arranged
that only one staff at a time can be
withdrawn from any given pair of
frames, it is evident that only one
train can occupy the ulock at any one
time. Our illustration shows a signal
man delivering a staff to the engineer
of a rapidly moving train.
Os late years, however, more and
more attention has been paid to auto
matic block systems and signals.
The development has been scarcely
less rapid than that of the electric car
or telephone.
In the automatic block system the
signals are moved by some power
such as electricity oi’ compressed gas,
and are controlled by the passage of
trains over the tracks by means of
electric circuits. The signals consist
of light arms of painted wood asso
ciated with frames carrying colored
glass discs which co-operate with a
lamp for giving night signals, the
whole being mounted at the top of a
mast or post, and connected with the
operating mechanism.
THE WEEKLY JEEFERSONIAN.
Two General Types in Use.
This operating mechanism has form
ed the basis of innumerable patents.
There are, however, but two general
types that are in extended commercial
use today. These are the pneumatic
or compressed gas mechanism, and
the all-electric mechanism. In the for
mer, the signal is moved by a piston
working in a cylinder, and in the lat
ter the motive power is furnished
by a small electric motor.
The supply of gas to the piston and
cylinder, or the supply of current to
the electric motor, is controlled by a
small magnet called a “relay.” This
relay is included in a circuit formed
by the rails of a block. When the
block is in safe condition for a train
to enter, the mechanism holds the
signal in position to indicate “clear
track, ’ but if there is a train in the
block the wheels and axles of the
train so affect the electric circuit of
the relay as to cause it to influence
rhe operating mechanism to move the
signal to the position indicating ‘ line
blocked.”
Since this relay circuit runs through
ihe rails of the track, and is led
over all switches that may be in the
block, it is evident that should any
thing occur to interrupt the continuity
of the track, the circuit of the relay
would be broken. This is arranged to
have the same effect on the signal as
the presence of a train in the block.
Shows Condition of Two Blocks.
The signals at the beginning of
each block are usually arranged to
snow the condition of the next two
biccks in advance. This may be ac
complished by providing two signals
on the same post, as shown iu our
view illustrating an installation on the
Lehigh Valley. The upper, or “home”
signal, corresponds to the adjacent
block, and the lower, or “distant” sig
nal, corresponds to the second block
ahead. The same result may be at
tained by employing a single signal
capable of occupying three positions,
;.s explained below.
When the two signals are used a
train in the adjacent block causes both
signals to extend their warning arms in
a horizontal direction, whicn is inter
preted to mean to an approaching
train ‘ danger,” “stop.” A train in
the second block causes the “home”
signal to assume an inclined position
oi about GO degrees, while the “dis
taut” signal assumes the horizontal
position. This means “caution —go
slowly.” With a single signal the
Horizontal position indicates “dan
gei I ” Ihe “caution” indication is giv
en by the signal assuming an Inter
mediate inclined position of 45 de
grees, and when the block ahead is
clear the signal arm hangs vertically
downward.
Ail automatic signals are arranged
sc that they will give a “danger” in
dication it any of the circuits or con
nections become broken or deranged.
In this way errors, when they oc
cur, are always on the side of safely.
The automatic signal not only indi
cates the presence of a train in the
block, but, as pointed out above, it
also indicates an open switch, or a
broken or displaced track, resulting
from any cause whatever.
Makes Mistakes Impossible.
Hence its vast superiority over the
telegraph block or controlled manual.
A signalman may fall asleep at his
post, and a train dash on to ruin, or
What It Is and Holv It Can Absolutely
Prebent 'Disastrous Collisions.
he may misunderstand his orders;
but the red and green eyes of the auto
matic signal are never closed, and the
ever-present electric current cannot
make a mistake.
The statistics regarding the opera
tion ot automatic signals indicate
that no more reliable means of guid
ing trains has been devised.
Fifteen months’ experience on the
Chicago and Northwestern Railroad
with 203 blocks shows that there was
only an. average of one false stop re
quired by the signals to 4,813 signal
movements. Furthermore, during the
seven years that these signals have
been in use there has been only one
false “clear” indication per 9,000,000
to 10,000,090 signal operations.
On the New York subway, proba
bly carrying the most congested traffic
in the world, where during busy hours
122 trains pass every sixty minutes, a
wonderful record has been made. The
hundreds of signals, aptly called the
guardian angels of the subway, all
perform their duty toward humanity
by protecting each car from being
run into by the following one, and
perform it with such almost infalli
ble precision tha(t there has been
an average of only one failure to half
a million movements.
There is, however, one advantage
peculiar to the manually operated
block signal. Experience has proved
that an engineer is less liable to dis
regard the warning in the presence of
a signalman. On the other hand, with
the manual or telegraph block there
are chances of error by the signalman,
the operator in advance, and the en
gineer, while with the automatic there
is only the engineer to err. Hence the
chance of error is as one to three
in favor of the automatic signal.
Human Element Eliminated.
In several modern installations,
moreover, the system has been so de
signed that the human element is elim
inated altogether by what is known
as the “automatic stop.” The de
vice consists of a little lever pivoted
on the road bed, and so connected
to a block signal that when the sig
nal is at “clear” the levei' is de
pressed, but when the signal indicates
“danger” the lever is raised and pro
jects above the track. Attached to
the airbrake system of the train is a
small valve which is so located as to
be in the path of the lever when
raised. If, then, an engineer attempts
to rim past a danger signal, the
brakes are automatically applied and
the train is brought to a stop. Had
this system been in use on the Bal
timore and Ohio Railroad the appall
ing accident at Terra Cotta would
have been impossible. The second
train would have been automatically
stopped when attempting to run past
the signal at Takoma.
The question of relative cost of au
tomatic and manual signals is large
ly determined by the length of block
necessary. Where blocks are short,
there is no question but that the au
tomatic is the most economical system.
A prominent signal engineer, speaking
on this subject, says: “It is very much
more expensive to install and main,
tain the manual (or telegraph) system.
The salary of two operators alone
would mean about $1,500 a year, and
say that you made these blocks three
miles long, this would cost SSOO a
year per mile for labor alone, not tak
ing into account the wear and tear on