New-York tribune., 1904-10-23
PNEUMATIC STOP SHOWING

10 stop within the block and within few feet OF
the home signal. II. then q following train should
overrun this home signal a collision would be the
result. With the overlap system, however. a train
may stop at any point IN a block section and still
have the home signal at a safe stopping distance
In the Of the train.
Conservative signalling IS all IN favor u the
overlap on account Of the safety factor. in case
the danger signal is overrun. but another consid-
GRAFTON for the use of the overlap in the subway
was the Of automatic train stops, which prevent
train being far past a danger signal. These
stops are placed AT the home signals. shown in
the accompanying pictures, and it is essential that
a stopping distance should be afforded in advance
OF home signal provide for stopping the train
10 which the brake had been applied by the
matte stoD.
TRAIN STOP IS AUTOMATIC.
The arrangement Of the train stop is such that
when the trigger which is shown rising at the
side OF the rail- lies fiat beside the rail the
home signal shows the block section ahead is clear.
1t is raised automatically by the passing Of train
IN the block and is kept raised until after the
block section is clear
When the raised trigger of the track stop is
struck by a train that has past the danger
signal two things happen automatically-the
emergency brakes are applied 20 stop the train
ana the electrical current is turned of the third
rail that the train cannot 80 ahead again until
after the mechanism OF the signalling station is
adjusted.
In the installation OF signal system for the sub
il Imperative 70 make the blocks as short
as consistent with safety in order not to cut down
the carrying capacity Of the express trains and
force them too far apart Block section
lengths governed by speed and interval between
trains Overlap lengths are determined by the dis
tance in which a train running a maximum speed
can be stopped. Usually the block section length Is
the distance between The signals, Plus the overlap
bat where maximum traffic capacity IS desired the
block section can be reduced 10 the length OF two
ovcrlaps. and this was the system adopted for the
careful Consideration was given to the overlap
necessary IN the subway. From tests OF the brak-
iue power Of trains computations were made 10
determine the distance in which trains could be
sroUped a various rates Of speed on level track.
WI corrections for rising and iaiii9g 70 grades up
10 per cent Speed curves were then plotted for
ahe trains the entire line showing Al each point
the maximum possible speed with the gear ratio
of the motors adopted. 4 joint ronsds-atlon Of
tic .peede, brakng Efforts. and pron-e ct the road
WIS then used 10 determine at each ana every
MONT on the Ire The minimum aloW~lIe distance
bet vgeen trains that the tratn IN l4c rear could
he stopped D. the autOmauc aIfitcal.3I- OF the
brakes before TeacninE train ~llcH, tt--sht he
e.andirg 81 slGral in advance: ih ositf words,
ne length - ia" overlap section was UeteI mined
hv tfe local conditions a. q rh point
CARE TAKEN FOR EXTRA SAFETY
To provide for adverse conditions. the aetua:
braking distance was Increased by % per cent for
example the brakine distance Of train moving Ss
miles an 4s5 feet: TITS would be increased 80