Re: (erielack) Interlockings and Terminology

["Tom Beckett" <tabeckett_@_stny.rr.com>]

Here's the definition of an interlocking from my LIRR rule book, but the
concept is universal:

"An arrangement of signals and signal appliances so interconnected that
their movements must succeed each other in proper sequence, and for which
interlocking rules are in effect. It may be operated manually or
automatically."

This is the definition of the machine itself, which is designed to prevent
an operator from lining up conflicting movements, thus causing a wreck. What
we refer to sometimes as "interlockings" are really interlocking
stations-places where an interlocking machine as defined above is in
service. This can be a junction-a place where two or more lines diverge,
such as CP Cass Street in Hornell; it could be a diamond-a place where two
lines cross, but do not connect, such as Rochelle, Ill, where the BN crosses
the UP. A junction may also contain both diverging routes and diamonds-BD in
Binghamton is such a place. A set of crossovers can be an interlocking
station, if an interlocking machine is in place there to control the lining
of switches and clearing of associated signals.

An interlocking can be controlled locally-from a tower, as has been
discussed here, in which case the towerman, or operator, lines up the
interlocking on the orders of a dispatcher. It can be remote controlled from
a central point, such as most of the major roads still remaining are given
to doing from far off dispatch locations, such as CSX in Jacksonville, Fla.
This eliminates the need for the tower and operator. An automatic
interlocking is not controlled by a dispatcher or operator, but by the
machine itself. A train approaching the home signal will set off a timer
when it passes the associated distant signal. If no conflicting move is
detected, it will clear the signal for the train after a certain amount of
time has elapsed. If there is a conflicting move, it will not clear the
signal until the other move has cleared the interlocking. This is generally
used on light density lines.

An important thing to remember here is control. The interlocking is a
controlled point on the railroad-note how Conrail referred to its
interlockings as "CP" something or other. This was because those locations
were under the control of a dispatcher or operator, who controlled the
movement of traffic through them. A simple hand throw crossover or siding
switch is not an interlocking, as there is no outside control-though some
are electric locked and can only be opened if the dispatcher releases them.
There are rules concerning non-interlocked switches to prevent accidents.

I hope that helped you make some sense of interlockings; anyone with
specific knowledge, please feel free to add to this or correct anything I
may have gotten wrong.

TAB
- ----- Original Message -----
From: "A Samostie" <quahog_@_sprint.ca>
To: <erielack_@_lists.railfan.net>
Sent: Wednesday, January 30, 2002 11:02 PM
Subject: (erielack) Interlockings and Terminology


> Dear Group,
>
> OK, this isn't specifically an EL-related question, but since the thread
> on interlockings is running concurrently, I hope y'all can help define
> some general railroad terminology.
>
> Just what makes an interlocking an interlocking (as opposed to a
> junction, a diamond, etc.)?
>
> I know that many "interlockings" were controlled by towers, and the
> various switches and signals were thrown by lever-actuated sheave
> cables.  But, many interlockings did not have towers.  For example...
> Warbasse Jct. (DL&W Sussex Branch crossing NYSW mainline, referred to as
> Hyper-Humus by NYSW).  Were there any interchange tracks at Warbasse, or
> just a simple diamond crossing?  If just a diamond crossing, why was
> this minor crossing called an interlocking?  There WERE sheave cables
> that connected the Lackawanna lower quadrant semaphores and the tilt
> board (later smashboard) on the NYSW -- is it the presence of cables
> that make it an interlocking?
>
> But, in some cases, where a branch joins a main line, it's referred to
> as an interlocking, where I thought it would have been called a
> junction.  Or, on Erie and DL&W, was the term "junction" only used to
> refer to an interchange with another railroad (e.g. B&O Jct., Andover
> Jct.)?
>
> Also, in some places, a crossover is referred to as an interlocking.
> Why?
> Does there have to be more than one switch to constitute an
> interlocking?  (Obviously, a hand-thrown switch to a spur or siding
> isn't an interlocking)!
>
> Cheers,
> Alan <quahog_@_sprint.ca>
>
>

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End of ErieLack Digest V3 #453
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