As always I will start with a little history. The interlocking currently known as CARROLL started life under the B&O as CX Tower. CX was an electro-mechanical plant of the type typically seen on the B&O with manually operated points and panel operated signals. CX was located south (railroad west) of 1950's relay/NX plant, HB Tower that governed the southern throat of the B&O's Camden Station. CX was also the junction between the South Baltimore Industrial Track and the Mount Claire Branch. The Mount Claire Branch was at the time a two track branch that allowed trains on the new alignment to Camden Station and the Howard Street Tunnel to reach the old alignment that terminated at what is today the B&O Railroad Museum. The old Alignment contained the Mt Claire Yard so CX was an important junction that allowed trains to reach this yard from the North. CX also provided a connection to what is now the South Baltimore Industrial Track, but then allowed southbound trains a routing to the Curtis Bay yard and industrial area w/o having to go through the Mt Claire Yard. To the south was the smaller Mt Winans Yard which complimented the older Mt Claire Yard.
Luckily pictures do exist online of CX tower as it appeared . Here you can see the cantilevered lever room design and the mechanical pipelines for point operation in this view looking north.
Here is a rear view. The bridge in the background is Monroe St.
Another rear view showing the I-95 viaduct which dates the photo to at least 1981.
CX Tower's Model Board with Baltimore to the right and the Mt Winans Yard to the left. You can see the tracks to HB Tower are bi-directional and the Mt Claire Branch makes a flat junction with the new Main Line. Also the interlocking lacks a full crossover facility.
As time marched on downtown Baltimore was facing severe Urban Decay as the Inner Harbor area, which like many waterfronts had been an industrial focused area, saw its business eroded by containerization and a general decline in manufacturing. In 1980 plans to build various freeways through the harbour were defeated and instead it was developed into what became the world's first post industrial tourist themed waterfront. By 1990 the City, unsatisfied with just an aquarium, maritime museum and a mall and still stinging from its Gridiron football team's decision to move to Indianapolis in the middle of the night, decided to build a new baseball stadium downtown on land that held the rotting remains of the former B&O Camden rail yards and pasenger terminal.
The stadium, appropriately called Camden Yards in the age before out of control corporate naming rights deals, would see the closure of the old B&O railroad station, but would also see the construction of commuter rail terminal more commensurate with the level of service as well as a brand new Light Rail line. While the new baseball stadium would usher in a return to designs reminicent of the jewlbox era and bring a thankful end to the reign of concrete doughnuts, the reconstruction of the passenger rail infrastructure downtown allowed the B&O successor CSX to have its adjacent interlockings, HB and CX Towers, to be rebuilt as well...at Taxpayer Expense.
Fortunately, in 1990 CSX was still installing B&O CPL signals on its former B&O routes so instead of traffic lights with Seaboard Railroad aspects we got one last gasp of position lights, this time on modern aluminum mountings and with solid state vital hardware. In 2007 the interlocking was altered again when CSX embarked on a capacity building project in the area. Fortunately due to the young age of the interlocking CSX opted to retain the CPLs, modifying some and installing one brand new mast. More on that later.
The tour will begin at the west end of the interlocking and work its way east. The entire set of photos can be viewed here if you want to follow along. Joining me on this trip was my British ex-Patriot friend who now works for New York City Transit because the cost of living in the UK is out of control
In our first photo we see the eastbound home signals for CARROLL interlocking. From right to left we have track 2, track 1 and a signaled siding. In 1990 CSX was not only still installing CPLs it was still re-using signal hardware too. In this case the original eastbound bracket mast for the old CX interlocking was retained as part of CARROLL. Since then because of Baumol's cost disease the cost of signal hardware in relation to the labour intensive costs of testing signal apparatus has fallen so it is now cheaper to buy new hardware, test it in situ and then throw out the old than to try to cut over old hardware onto new logic. This is even the case where the signals being replaced are nowhere near being life expired. The eastbound signals at CARRROLL are a good example of this effect as the bracket mast used old CX hardware when being installed in 1990, but when the dwarf signal off the siding was replaced in 2007 it was cheaper to install a new mast.
The bracket mast is of the typical B&O type. When the new Darth Vader mast was installed in 2007 the relay case for this end of the interlocking was also replaced with this raised variant that is flood (but not graffiti) resistant. Apparently the vital hardware has also been fitted with extra beebop. The bracket has the dangerous feature of causing me to take my eyes off the road when I pass by on the I-95 overpass directly behind it.
If you think these signals look familiar you would be right! A competing signal website uses the eastbound bracket CPLs at CARROLL as an exemplar for a comprehensive primer on B&O CPL signals. Because BAILEY interlocking is back-to-back with CARROLL, and because BAILEY involves slow speed routes the track 2 CPL is one of a special breed of CPLs that contain all 6 orbitals. As one can see on the essay about BAILEY and DORSEY back to back mainline crossovers will give one 4 of the 6 orbitals. 12 o'clock for Straight, 10 o'clock for Approach Medium, 6 o'clock for Medium Clear and 8 o'clock for Medium Approach Medium. Add in the slow speed route at the next interlocking and you get the 2 o'clock orbital for Approach Slow and combined with an immediate medium speed crossover and you get the coveted 4 o'clock orbital for Medium Approach Slow.
At this point they were displaying Stop. The only thing preventing the track 2 CPL from being a "full" CPL is the lack of a lunar white Restricting \. The signal instead displays a white marker over - - for Stop and Proceed aka Restricted Proceed. The only reason the #1 track signal is not like its brother is because of an intermediate home signal on track #1 that we will see shortly. The eastbound signals at CARROLL are the only ones in the interlocking that are not approach lit.
Closeup of the 6 orbital track #2 signal. The (D) plate is for the Delay in Block rule that marks this signal as a Distant for push-pull commuter trains that make a station stop in the block. The (D) is required even if there are no station stops to which it might apply.
The track #1 signal only has the upper row of orbitals because there is an intervening mast signal located about 500 feet east that is before any diverging routes are encountered.
Rear angled shot of the bracket CPLs showing the finial capped mini-masts and the read of the CPL fixtures. The junction box in the middle of the targets is the third and final major design type. They are different from both the original "clam shell" type and later GRS logo box in that they are large and from a generic manufacturer.
The eastbound Darth Vader mast for movements off the signaled siding has three heads with lamps in the order of R-RL-RY. This allows the signal to display Stop, Restricting and Slow Approach. The mast does not need to display anything more due to the presence of the aforementioned intermediate signal.
Side view of the Darth Vader mast showing just how busy that "Bonk" tagger has been. This mast is now non-standard as CSX prefers to group its slow speed indications into bottom head.
Rear view of the eastbound home signals. In this similar view taken in 2004 we can see a the CPL dwarf and split point power derail still governed the siding track. The derail was removed when the track was upgraded from a yard lead to a signaled siding. The siding ends at the #3 switch which is just in front of the #1 facing crossover between track 1 and 2. You can also see from these pics a 4-track bridge over a small creek, the 4th trackbed being unused at this time.
Ghosts of the old CX Tower still exist in the form of concrete footings for the mechanical point pipelines.
In contrast to the fully equipped CPL on the bracket, the mast governing trains off of the Mt Claire Branch has no orbitals, just a simple 3-aspect CPL target.
Here is a closeup of the central target target for the Mt Claire Branch mast. This target is clearly made from steel unlike the newest CPLs which don't seem to corrode.
Rear of the target showing the new style GRS branded junction box. Behind the Mt Claire Branch mast is the power supply for the electric point heaters.
The South Baltimore Industrial Track rates a Medium Speed turnout and therefore a 6 o'clock orbital, but it joins into track 2 that has no intermediate signal. Therefore trains making a diverging movement at BAILEY would get a Slow Approach Slow instead of Medium Approach Slow. Since that routing would be highly unlikely the 4 o'clock orbital was never installed.
Close up of the rear of the mast's target. You can see an original style junction box that is surprisingly free of rust.
Side view showing one of the interlocking's relay huts in the foreground standing on the approximate location of CX tower.
View looking east past the former site of CX tower showing the junctions of both branch tracks and the intermediate mast on track 1.
The Mt Clair Branch joints the main at the #5 switch directly in front of the intermediate mast signal. I have no explanation as to why the interlocking was set up this way with this intermediate signal in the middle of the plant only on track #1. One hypothesis could be an attempt to allow commuter trains to travel at full speed to the eastbound home to minimize delays to any through trains washing to get past.. It's presence sure makes things interesting due to the very short signal distance between the eastbound bracket and the intermediate mast.
The track #1 eastbound mast has nearly a complete set of orbitals with 5. It is Missing the Approach Medium 10 o'clock orbital because at BAILEY the only option is for a Slow Speed route. Still a 5 orbital CPL is no slouch and I don't know of many like it.
The black backing paint has faded somewhat on the aluminum mast. Unlike the older steel masts the loss of paint just decreases the aesthetics instead of the corrosion protection.
Close up views of the intermediate mast's target and orbitals showing the length of the sun visors. It appears that all of the CPL components were constructed of aluminum at this point compared to the older pressed steel units. Shame they became a dying species so soon after.
Rear view showing the 3rd generation junction box. Sort of wound up shooting day for night here with with the position of the sun.
A slightly better lit view of the rear of the track #1 mast.
All of the point machines are GRS Model 5F electrics.
The east end relay hut is the one that bears the interlocking's name.
Wide shot showing the relay hut and an adjacent goods track that serves local industry. Downtown Baltimore provides a nice backdrop for the interlocking.
Zoom view showing the alignment of the #9 turnout with the Mt Claire Branch, its signal and the intermediate mast.
On the Camden Line route, CSX only bothered to install point heaters on a subset of its points/interlockings since due to the large number of interlockings they can run snow plan that restricts use of non-heated turnouts in inclement weather. CARROLL is a micro-chasm of this philosophy as most of the points are not equipped with heaters except for a few critical ones. The rest have to make do with decidedly low tech smudge pots.
The #11 switch is the one that has been equipped with an electric resistance type point heater. This is due to the fact that trains diverging here are committed to going to the stub end Camden passenger station. This is the track that was added in the ~1991 rebuild to support the new commuter train station. In order to ensure that trains can be switched between the Baltimore Belt Line and Camden Station the #11 switch gets electric heaters. This is also a limited speed (45mph) switch.
Well we have come to are grand finale. Here we see the westbound home signals and the PSR signals for the sharp curve before BAILEY interlocking. The cantilever mast is of an early aluminum tube type that now have become standard in North America. The mast on track #2 was installed new in 2007 to replace an earlier CPL mast. You can see the lights of the baseball stadium just under the leftmost signal.
A closer view of the rear of the cantilever mast. The tubular members are thinner than they are today.
Rear of the new track 2 mast signal. The CPL components are freshly painted and the ladder is of a wider modern type. The structure of the mast has not been painted black for contrast as had been done in years past.
This signal was installed in 2007 from parts salvaged in house from decomissioned CPLs. As a result it uses the second generation GRS branded junction box as opposed to the new ordered boxes seen on the 1992 equipment.
Alright, enough beating around the bush. Here is what you have all been waiting for, the westbound signals at CARROLL. Because of the two un-signaled industrial tracks all three of the CPls have Restricting \ indications. This means they all have full central targets. The track #1 cantilever signal also has the complete compliment of 6 orbitals. A full central target plus a complete set of orbitals gives one a "Full Complete" B&O CPL, the only one in active railroad service in the world.
What is perhaps even more remarkable is that these signals didn't use to be that way. Back before 2007 the westbound signals at CARROLL were nothing remarkable. Just look how they have plumped out since the capacity expansion project.
What made all the difference was the yard lead that was converted into a signaled siding and a rebuilt WEST BALTIMORE interlocking back-to-back with CARROLL that I previously covered in another essay. For the CPL governing westbound movements on track #1 the signaled siding added the 8 o'clock orbital for Medium Approach Medium. The 10 o'clock Approach Medium orbital is due to the short signaling block between West Baltimore and the Lansdowne interlocking beyond it. What added the 2 and 4 o'clock orbitals is still a mystery for me. The new cantilever mast at WEST BALTIMORE has a lowest yellow lamp available on the siding track which is either used for Slow Approach or Medium Advance Approach, but seeing as how nether of the main tracks have space provided for Slow Approach makes me doubt the Medium Approach Slow indication would be necessary at CARROLL. Also the lack of a slow speed indication on the main track seems to remove any need for the Approach Slow aspect.
Anyway, I guess the good news is that those orbitals were provided for some reason, even if I have yet to figure it out. The result is that an example of a Full Complete CPL came back from extinction after the last one at LAUGHLIN JUNCTION vanished in 2005. Of course its only a partial replacement for the side-by-side Full Complete modern bracket mounted CPLs at Curtis, Indiana that were removed in 1999.
The train that springs forth from the #11 switch is called MARC 1 (MARC is the commuter rail authority) and is only used by MARC trains to Camden Station. It too gained an extra pair of orbitals to fill out the lower half. One advantage to B&O style CPLs is that often signaling changes only require the addition of orbitals instead of new signals or signal heads. Unfortunately remember what I said about the costs of hardware vs testing. In this case we sure lucked out that for whatever reason it was decided to retain the CPLs.
The only thing that prevented a pair of Full Complete CPLs at CARROLL is that WEST BALTIMORE interlocking is not in service on track 2 so there is no need for the Approach Medium 10 o'clock orbital...which is a tad ironic as that is the most common off center orbital
Angled view of the rear of all three westbound signals showing the differences between the second and third generation junction boxes.
Here is the pair of expanded CPLs on the cantilever mast. I still need to figure out why they need that Approach Slow aspect. There are no routes at WEST BALTIMORE interlocking that appear to need it. There are some short signal spacings there, but going by the signals provided at WEST BALTIMORE they do not demand an Approach Slow.
Close views of the rear of the cantilever CPLs. I love how the maintainer ladders are basically consumer grade extension ladder bits.
The position of the sun was being a bit of a pest so I decided to make lemonade and made some cool solar eclipse shots with the CPL target
After visiting CARROLL interlocking I walked about 1/2 mile to the west to the 3-track B&O CPL gantry at BAILEY. By that point a signal had been displayed for an eastbound move on track #1. The crossing gates kept going up and down due to road salt shorting the track circuit and I eventually gave up waiting for the train...which did manage to show itself about 15 minutes later when I was waiting for a light rail train. Anyway I wanted to show the routes available at BAILEY interlocking that motivated the 5 and 6 orbital eastbound signals at CARROLL.
From right to left we have Track 2 which offers a medium speed route to track 1 or a straight route to the Locust Point Branch. Because of a 1700 foot block to the next signal the signal can display Slow Approach and motivates the Approach Slow and Slow Approach Slow on the eb signals. On track 1 there is a Straight route or a Slow speed route to the Locust Point Branch. Short blocks on either route result in Slow Approach. Finally on MARC 1 there is a Medium Speed route to track MARC 2 as well as a short signal block past the second signal for the Approach Slow and Medium Approach Slow signals.
Anyway that's pretty much it for today. I hope you find this informative and if it has inspired you to visit Baltimore here is a very thorough railfan guide including hotel information. ;-)