Again if anyone is interested in the official interlocking diagrams you
can download them here.
http://www.multimodalways.org/docs/rail ... %20Charts/
You'll want the 1998 Pittsburgh Division one.
ALTO marks the transition from a two track railroad running under Rule 261 on both tracks, to a three track line with single direction Rule 251 on the outer tracks and Rule 261 on the center track. ALTO was arranged, or possibly re-arranged back in the Penn Central era, to allow easy access for Amtrak trains in both directions to access the station platform(s) located on the north side of the tracks. The 31 switch allows westbound trains to continue either on the 251 track 3 or the 261 track 2. Eastbound trains are given a straight shot to the platform off of track 2. Passenger trains heading east on track 1 must first cross to track #2 at SLOPE. Anyway here my train departs the Altoona station and takes the #31 switch set reverse to track #3.
Here we see the reverse direction 20R dwarf signal for movements on track 1. This signal is controlled from the main machine in ALTO tower. To the right we see the helper pocket track and its eastbound 32R dwarf signal. The pocket exists between that signal and the PC era signal gantry.
Ironically one of the most iconic structures at ALTO appart from the tower itself wasn't even original to the interlocking. The 5-track beam type signal gantry was installed during the Penn Central era in conjunction with a PennDoT bridge and highway project in the area. The gantry supports three high signal masts governing westbound movements on tracks 1 and 2 as well as the helper pocket which are worked from levers 2R, 6R and 8R on the main machine.
ALTO tower itself posing by the westbound lattice signal gantry which probably dates from when the tower was built in the early 20th century. Sometime in 2008 the tower was given a fresh coat of gray paint, but this investment was not a signal of any sort of longevity as you all now know the tower is scheduled to close sometime in the next year.
Here we are looking at the 6 track eastbound gantry at ALTO, which only supports two high signals for tracks 1 and 0. The slow speed diverging aspects on both are for movements onto the yard leads which are in fact signaled to CP-WORKS as a controlled siding.
Here we are looking at the 1sw and my extension the entire ALTO facing point ladder which runs from here to the yard leads at the other end of the interlocking. As ALTO is basically a yard-terminal tower most of its movements involve trains either passing straight through or heading into/out of the yard, hence the ladders that head to that side of the track. As expected ANTUS interlocking can be considered the reverse of ALTO.
Here we see the eastbound home signals for ALTO on tracks #1 and #2. As expected the reverse direction track 1 signal is a dwarf and the bi-directional track 2 signal is a mast. This zoom view provides an interesting prospective on the layout of the entire interlocking.
CP-SLOPE is less than a mile west of ALTO, but as it suggests it represents the beginning of the stiff grade up and over the Allegheny Front, cultimating at the PRR high point at Galitizin and the famous Horseshoe Curve. The interlocking was simplified and put under remote control of ALTO in the 1950's and from that point on was only in service on tracks 0, 1 and 2. Here we see the rear of CP-SLOPE's westbound signal gantry which also hosts the 2371 automatic signal for track #3. The 8L track 2 signal is only equipped with a restricting \ as any diverging route there would result a reverse direction move on the 251 signaled #3 track. Also visible is the 6L reverse direction dwarf on track #1.
Here we see the relay hut at CP-SLOPE which is in the typical pre-prefab bungalow style. You can see the outline of the larger PRR style SLOPE sign surrounding the smaller blue Conrail one. This interlocking as listed as being under direct wire control from the machine in ALTO tower, but I suspect that means the control is direct wire (as opposed to pulse code) with vital interlocking components in this relay hut. Also notice the #7 switch to the right which allows eastbound trains on track #1 to crossover to track #2, a move not supported at ALTO.
Here we see the eastbound signal gantry showing off the 6R and 8R signals. The road bridge in the background has been a very popular railfan location with cutouts in the protective fence for people to take pictures through. This will be the site of the new ALTO interlocking which will more resemble a traditional interlocking without the pockets and such of the old one. This is almost a what's old is new again situation as before it's remote control to ALTO, SLOPE was a crossover of that style.
Closeup of the 6R and 8R signals. The 8R is of a new Safetran design that was installed sometime in the Conrail era.
Arriving at the first automatic signal west of the Altoona complex we can now see how the automatic signal numbering has not changes from the newer Conrail style to the original PRR style. In case you forget the Conrail style uses while Milepost appended with track number and direction. As in 1231-E. The PRR system used milepost to the nearest 1/10th mile with eastbound signals being the nearest even 1010th and westbound using the nearest odd 1/10th and the signals having the same number across all 4 tracks. So here we see the 2384 eastbound automatic signal. The signals are dark because all the PRR signals up the east slope are approach lit.
Both eastbound signals are able to display Approach Slow due to the short block distance between CP-SLOPE and ALTO resulting in an Approach Slow-> Slow Approach->Stop progression. This is to ensure trains are under control on the steep downgrade. The lower | on the track #1 signal is for the medium speed diverging move to track #2 at CP-SLOPE. This signal bridge is currently scheduled for replacement and re-signaling as part of the ALTO replacement project, but in this photo from 2006 we can see the signal lit up and the train in questing getting an Approach Slow indication for a stop at ALTO.
Regrettably the assault on the PRR east slope has been long going on for some time now. Between 2007 and 2009 all of the signal bridges between MP 238 and CP-MG were systematically replaced with NS style Darth Vader cantilevers. In a partial consolation, one of the signals appeared to have the vital equipment replaced, just the PRR PL signals and gantry structures. Here we see the replaced 2398 signal showing off NS's love of the cantilever mast which in this case extended across a 4 track right of way. The footings of the old signal are in evidence and the approach lighting is in effect.
As I am sure nobody wants to see a bunch of Darth Vader signals here is a 2006 view of the 2398 ssignal bridge. This is of the older style lattice type which have been frequent targets for replacement due to age and structural integrity issues. The large subsidiary indicators for the tracks 1 and 2 signals are to alert the crew that a dragging equipment detector has been activated and the train needs to be stopped and inspected. This was a holdover from the pre-radio readout type detectors.
Again, here is the original position light as seen in 2006. Note the style of the access ladder and the apparent lack of any structural issues.
I refer to this signal in the past tense because in 2009 when it was rather heartlessly replaced by a NS Darth Vader cantilever, the foundation of which can be seen here in this wider shot. While this signal gantry was preserved at the Railroader's Museum in Altoona, it is a shame that NS could not more appropriately honor the legacy of the PRR by either installing new PL units on the replacement signal or just recondition the old gantry in place.
The 2426 automatic around the far side of the curve and distant to CP-MG was also included in the 2009 signal massacre. This signal is in a very inaccessible location and is rarely photographed.
Here we reach CP-MG, which until 1994 was the site of the active MG tower. MG tower was constructed in 1944 as part of an emergency War capacity improvement programe to relieve congestion on the east slope. MG, which stands for "Mid-Grade" was just that, a new crossover in the middle of the steep grade to allow faster trains to duck around slower ones. Here we see the westbound signal gantry from behind. This was the last model of PRR lattice signal bridge with the solid steel end caps.
CP-MG showing the 7sw. MG is a full 3-track crossover with all 4 turnouts being operated by pneumatic point machines. Also note the wrong direction dwarf signal on track #1.
Despite the war a lot of effort was put into MG tower, with modern brick construction and a throwback design that emulated some of the older towers and station buildings in the Horseshoe Curve area which themselves were based on the sorts of buildings seen in the European alps. The two wings of the tower housed the compressor gear for the pneumatic point machines. The interlocking plant was built as a full 4 track crossover with bi-directional signaling on what was then #3 track. A 23 lever US&S Model 14 with 12 working levers was installed.
MG held on until the mid 1990's along with AR, MO and SO towers. It was finally closed when the line was being upgraded for double stack operations. Open part time MG was always a challenge to get to, especially in the winter months as the only access is via a winding dirt road. As other railfan locations have been ruined by re-signaling MG has become increasingly popular with the 4x4 / GPS equipped crowd. In this picture note the second pipe running under the air pine which carries natural gas for the point heaters.
We leave CP-MG at its eastbound home signal, in this case displaying a Clear indication on its track 1 home signal. While the westbound signal bridge is in its original 1944 configuration, this one was updated in the 1980's when the 4th track was removed. Again note the dwarf signal for reverse direction moves on #3 track.
Here is the 2444 automatic signal bridge and distant to CP-MG. As of 2011 this and the other western east slope automatic gantries have not been replaced.
The 2454/2455 automatic is special as it used to be the distant to BF interlocking, which was a trailing point ladder east of the Galitizin tunnel complex. That interlocking was removed during the 1980's rationalization project. Today the 2455 signal is the distant to CP-UN and sports both approach medium and approach slow indications for the crossover and loop routes respectively. Also not the "Galitizin" HBD-DED co-located with the signal.
With the removal of BF interlocking a supplemental automatic signal was installed on #1 track for eastbound moves only. It is completely in the Conrail style and numbered 2461E.
The PRR Galitizen interlocking complex consisted of 4 interlockings. Those two that still exist, UN and AR, will be covered in the next part. However east of the summit, BF and SF, both still deserve a mention. SF interlocking was where the auxiliary freight route rejoined the Main Line. This auxilliary route bypassed Altoona completely and traveled from just before the Spruce Creek tunnel (where CP-TUNNEL is today) through Hollidaysburg and then up and around the Muleshoe Curve. The only evidence of SF's existence is this track #1 flyover bridge just before the summit tunnels.
It is only fitting to wrap up this section of the PRR Main Line signaling survey with a shot of the High Point of the Pennsylvania Railroad at Galitizin, PA which is 2167 feet above mean sea level. For those of you who don't know the three track complex was reduced to 2 during the 90's double stack clearance project. The old Galitizin tunnel to the left was closed and the Allegheny tunnel in the center expanded to accommodate two tracks.