Western Railroad Discussion > SP Block Signals - 80s and 90s

Correct me if I'm wrong, but wasn't SP's standard design for new signals right upto the UP acquisition based on the triangular tri-color signal? When did the SP quit using searchlights for new signals installations and switched over to this tri-color design?

We started seeing them mid-1990's here on the Coast Line. All of the ABS was replaced by CTC between Lick and Gilroy, and so went the searchlights.

While I don't know the exact date, I know that SP was installing the new tri-lights in the early 1990's. They installed several on what is now the Metrolink main line north of Los Angeles.

First one I saw was in 1986 on the East Valley line near Sheridan, CA.

When SP replaced their semaphores around Elko, NV in the mid 70's, they installed vertical tri-lights.

When they installed CTC on the Palmdale Cutoff, they had a mixture of searchlights and vertical tri-lights mounted back to back. Not sure when CTC was installed, but my best guess is late 70's or early eighties.

The SP began replacing its semaphores in Nevada with tri-lights in 1974. A 1976 photo showing this replacement in progress near Osino, Nevada can be found on pg. 38 of the January 1978 issue of Trains.

CTC between Mojave and Palmdale was installed in 1980.

The Triangular Tri Lights are/were a sign of the times since many insiders call them Bankruptcy Signals (hence the Rock Island). Of course the Newer Vertical Signals the UP and BNSF are installing are pretty cool with some character, but I like to call them "FLYING NUNS".

vry wrote:
Of course the Newer Vertical Signals the UP and BNSF are installing are pretty cool with some character


I can think of only one characteristic: they're ugly! Long live the searchlight.

The triangle signals mounts came with the Rock Island Tucumcari Line purchase. These are RI signals and with the trackage came the stores department supplies which was a large supply of these signals. The searchlights like the semaphores, having moving parts that work together make them more expensive to maintain. The tri lights have individual parts for each color, easier to maintain.

ABS = CTC I thought?? Automatic Block Signalling, is Centralized Traffic Control.

Rob

Weren't the triangular tri-colors standard on DRGW? I had always assumed that, since they began appearing here in California about the time of SP+DRGW.

Freddie wrote:

> Weren't the triangular tri-colors standard on DRGW? I had
> always assumed that, since they began appearing here in
> California about the time of SP+DRGW.

No, I think that was just a coincidence. The Rio Grande always had vertical tri-colors and searchlights. I think the triangular tri-color thing started right after the SP acquisition of the Golden State Route, as somebody else previously stated.

slr62 wrote:

> ABS = CTC I thought?? Automatic Block
> Signalling, is Centralized Traffic Control.

There are other three letter acronyms for
CTC (Santa Fe called it TCS), but ABS is not
one of them. ABS and CTC are not the same.

Automatic Block Signalling, as the name implies,
is fully automatic. The dispatcher does not
control signals or switches. The switches are
usually hand-throw or otherwise controlled in
the field, and the signals respond automatically
to track occupancy in the blocks ahead of them.
ABS signals do not convey authority to occupy the
track; that comes from the dispatcher via a track
warrant, block authority, or in the old days,
train orders.


In CTC, the dispatcher controls the signals, and
usually the switches, at locations called control
points. The signals DO convey authority to occupy
the track ahead. Intermediate signals between
control points usually operate automatically
based on occupancy, similar to ABS, but the
system is still considered CTC throughout.

There was a long thread on ABS/CTC a few
days ago:

http://www.trainorders.com/discussion/read.php?f=1&i=161060&t=161060

I agree that the timing is about the same as the take over of the Rock Island, but the signals are not the same. The Rock had old GRS triangular signals, and the SP was installing SafeTrans (which can be configured vertical or triangular). I doubt that the RI preference had anything to do with SP's choice, and it definately was not availability of parts, because they are not interchangable. The first place I saw a triangular signal on the SP was a replacement for a semaphore in Oregon.