The layout is fairly simple. The ATSF and Alton lines run roughly north-south through the City of Joliet and come together in to an elevated 4-track corridor that then cross the former Rock Island main running east-west at a diamond crossing. This elevated diamond crossing and rail corridor was part of a 1912 project to construct a new Union Station at Joliet serving all three of the major railroads in grade separated splendor. Along with this station came a new interlocking tower to control it which was UD which I assume stands for Union Diamonds or something like that. Like the other Chicago area towers diamonds were the name of the game and in its heyday UD featured a 4x4 grid of diamonds where the 2 main lines met. However today that has been reduced to a 4x1 as the Rock Island really took it on the chin, eventually going bankrupt and nearly being abandoned.
Even tho the 3 main lines were separate UD contained ample crossover facilities between the lines that were used to varying degrees. People might know UD from old pictures usually involving the Southwest Chief and the large signal gantries spanning the parallel main lines covered in semaphore signals. Today the semaphores are long gone, but some of the crossovers do still exist even if they aren't all used much. Today UD sees freight service on all of its lines, but primarily the BNSF route which is a major double stack intermodal route into the BNSF Corwith yard complex. The former Alton line does see some through fright, but it is largely a passenger route with a peak period METRA Heritage service from here to Chicago Union Station , but also Amtrak "Lincoln Service" to St Louis along with the Texas Eagle long distance train. This line is being upgraded to a high speed corridor with 110mph operation. The crossing route sees all day METRA service as part of their Rock Island district so Joliet serves as the terminal of two independent Metra services.
This tower is officially located in the "Western Region" of the United States where I am not properly qualified so I am hazy on various details such as ownership or when parts of the interlocking were modified so I apologize in advance for any missing or inaccurate information about this tower. The following description will contain two primary sources of photos. The first come from an Amtrak trip I took to St Louis in 2005 and cover the Alton alignment in both directions. The second were provided by a railroad affiliate and detail the inside of the tower taken around 2007 or 2008.
I also do not as of yet have a historic interlocking diagram for UD tower, although that might change and I would post it right here in an update.
You can see the entire set of photos here which I have left in their original resolution to help show off the detail contained within. Let me know if you would prefer that I linked to the images directly so that one's browser can scale them properly.
We will begin on the Alton Main running northeast to southwest (railroad east west). Here we are facing UD interlocking (the tower is visible in the distance) on the Alton Main just before it ramps up to the grade seperated alignment at the station. The signals before us are the start of the CN controlled CTC territory. Between here and the limits of UD the line could be considered under ABS rules.
Over on the left we see the rear of UDs home signals and the BNSF ABS entrance signals. At the time the BNSF main was running under single direction ABS rules east of here with a pole line for communications, however overhead photos confirm the both the searchlight and target type color light signals have been replaced by bi-directional traffic lights. Lever numbers are 10 for the reverse direction dwarf, 8 for a straight route on the mast and 6 for a diverging route (which was originally provided by a subsidiary signal).
Moving a bit further and looking back away from the interlocking we see the rear of the westbound home signals on the Alton into UD. The mast signal has been replaced by a modern traffic light type signal which the reverse direction dwarf is an older US&S N-2 unit. Lever number for the dwarf is 11, straight route on the mast is 2 and the diverging route is 3 or 4 depending on an Alton or Santa Fe lineup.
Searchlight automatic signal 72 acts as an exit signal and governs the short distance between UDs limits and the start of CN CTC. We can also see a facing point turnout over on the BNSF main which is worked by levers 14 and 15..
Moving on we find UD's remaining double-slip switch which allows trains on the BNSF route to access the Alton Line. As the tracks curve north of the tower the "diverging" route actually appears to continue on straight. The point of this ladder and a matching one on the opposite side of the interlocking plant was to allow passenger trains on the Alton to platform on the holdout platform at Union Station. For whatever reason this strategy is no longer employed at UD and the matching double slip ladder on the west end of the interlocking was actually removed.
UD is a heavily zoned interlocking with multiple signals along each route. The doubleslip switch and the BNSF facing crossover are in the eastern zone. to the right we can see a rock Island style target color light signal that marks the entrance to the central zone that handles the diamonds. This is a Rock Island style as the US&S supplied triangular target signal has large shade hoods which was a forerunner of today's Darth Vader signal. The doubleslip turnouts are control be levers 40, 41, 43, 47 and 48. The Rock Island style mast is 60 and the dwarf across from it is 59.
>Looking back in the other direction at the doubleslip we can see two floating dwarfs on the reverse direction tracks. These are numbers 36 (Alton) and 31 (Santa Fe). I am sure these used to protect some form of additional turnouts or whatnot.
Here we see UD tower with the east signal gantry. One interesting thing is the presence of subsidiary signals to provide call-on aspects for trains. The BNSF eastbound mast has two heads for the diverging route onto the Alton. This is route signaling territory so that is why the signals here have so much fewer heads than on eastern railroads. From left to right we have the eastbound Alton signal, lever 52 main and 54 subsidiary, then the reverse direction Alton signal (a "high" dwarf) controlled by lever 55, then the westbound Alton "central zone" signal under lever 61 then the eastbound BNSF signal under lever 57 for the main route and levers 56 and 58 for the other two Alton routes.
In this picture we can also see the arrangements for passengers boarding the trains on the Alton tracks. Due to the lack of any under or overpasses trains on the BNSF must be held to allow passengers to board or alight from trains via the duckboards.
Eastbound view of the east gantry showing the front face of the two headed BNSF signal, the eastbound Alton main signal and both subsidiary signals.
The tower is located at the point of the diamond crossings across from the Union Station building which was last renovated around 1990 and apparently is quite nice inside despite the primitive platform conditions. The lever 60 signal on the BNSF is in place to allow trains to be held clear of the passenger platforms so passengers can cross the tracks. There is a closer signal on the edge of the platform, 64, that actually protects the diamond. On the eastbound tracks we see reverse direction dwarf signals 63 (BNSF) and 62 (Alton).
Side view of UD with a Metra MoW truck painted to look like a high visibility vest. The tower is quite long to fit in the lever frame and also tall for all of the relays in the first floor.
Wider shot of the tower showing the formerly 4-track Rock Island right of way which has been reduced to a single track.
UD and the diamonds with the 62 signal in the foreground. The tower is of a poured concrete construction with a nice bay window for the operator. UD has suffered from Tower Window Syndrome with most of its grand double hung windows having been replaced with small cheap modern ones...or plywood.
Here is another closeup view of just the diamonds. Back in the day there used to be 16 diamonds here in a 4x4 grid.
Never a dull moment at UD. Moments after my Amtrak train cleared the diamonds an outbound METRA commuter train was signaled across the 4 main tracks to platform at Union Station. Yes the 63 signal only has one lamp, it either flashes red for Restricting or is an LED jobber that can also display yellow.
UD in the opposite direction showing the new Minor League baseball stadium that was built as part of an urban renewal project. Today the tower and classic platform area are both under threat by plans to make a new transportation center, remote control the crossing and separate the freight line out somehow.
Wider view of UD and the Union Station platform area. The large platform between the BNSF tracks was built to handle the more important ATSF passenger traffic including the Southwest Chief. However today no passenger trains use that line (the Chief was re-routed via the former CB&Q main to connect with the ATSF main past Galesburg, IL due to a move to Union Station in Chicago) and the intermediate platform is much neglected.
Moving past the diamonds we reach the west gantry which marks the division point between the central zone and western zone of the interlocking. The crossover in the foreground runs to the Rock Island district via another connection not visible here and is used by the small number of Metra Heritage Service trains on the Alton to access the storage yard which is located on the Rock Island line. The crossover is worked by levers 74 and 75. The 4-lamp signals are what used to be main-subsidiary combinations with the Call-On lamp (probably lunar white) being added to the main signal. The two signals facing us in this photo are the 89 (Main) and 88 (call-on) for the Alton and the 91/93 on the Santa Fe.
Eastbound view of the gantry showing the entrance to the central zone of the interlocking and the lever 74 worked connection to the Rock Island line. Running down the center of the tracks is the which direct wire control wire bundle suspended between concrete support posts that connects the field equipment to the power frame in the tower. Signals visible are 86 (Main) and 85 (call-on) for the eastbound Alton, 83 for the reverse direction Alton and 87 for the Santa Fe.
Moving further west we find the 105-106 turnout between the BNSF main tracks and the 97 dwarf on the reverse direction Alton. All these extra little signal zones make reversing trains for Heritage service much easier. Beyond the turnout are the new bi-directional CTC entrance signals and westbound home signals on the BNSF line. Behind the CTC signal displaying a Clear is the lever 142 home signal.
Moving along west we find the 130/131 facing point crossover seen here in the reverse position after having been traversed by my Amtrak train. This crossover was actually paralleled by another doubleslip ladder similar to the one on the east end of the interlocking that I mentioned before and served to allow Alton trains to platform on the holdout platform at Union Station. For whatever reason this ladder was ultimately removed you can still sort of see where it was just beyond the 3-headed signal which was controlled by levers 140, 141 and 147. Why the parallel 103/131 facing point turnout was considered necessary I do not know. The 143-145 eastbound home signal on the BNSF main is also visible.
The 130-131 crossover in the other direction. You can see here how the BNSF main ramps up to the grade separation and also how the two main lines split apart beyond the interlocking limits.
Finally we reach the end of UD interlocking at the eastbound home signals. Again we have a 4-lamp main call-on combination on the eastbound track and an N-2 dwarf on the reverse direction track. The main signal uses levers 154 (Main) and 153 (Call-on) anf the dwarf is lever 152.
Alright, that's all for the interlocking outside the tower so now we move inside to the operator's level in UD. Here we find a wood paneled GRS Model 5 pistol grip interlocking machine with 224 levers. Here we are at the lever 1 end looking railroad west past the operator to the lever 224 end. The interlocking machine is divided into 4 stations, which back in the day were probably each staffed by a leverman. I should also point out the lack of an illuminated diagram, instead trains are announced by the semaphore style track circuit indicators on the fall wall, or by lock lights on the interlocking machine.
Behind the machine is a typical GRS amp meter which alerts operators to the status of the high voltage point machine power which is routed through the interlocking machine itself.
Here we see operator station number 1...and I guess there is a form of illuminated diagram, just not the dynamic kind. Three of the stations show a diagram of the Alton/Santa Fe portion of the interlocking and the fourth shows the Rock Island portion. As can be expected most of the levers are now painted white as spares, but there is still a good amount of active levers.
Closer view of station 1.
Here at Station 2 we see levers 57 through 102. We also are provided with a very good view of the current track schematic for the interlocking which dates to when Southern Pacific owned the Alton route in the 1980's. Also note how the 75/76 turnout has two lever spaces on the frame, but only one lever. This has to do with the GRS "dynamic indication" system which requires individual internal lever equipment to detect the position of the field switches. Lever positions 98 and 99 have been taken over as BNSF CTC indications that show when certain routes out of the interlocking are cleared for movement.
Above leverman station 3 we see the logos of the three railroads that operated the plant in the 1960's.
Here we are looking back at stations 1-3 showing the track circuit indications on the east wall.
Stepping back we see all 4 stations including a lock lever that I am not sure goes to what.
Station 4 has probably seen the most severe impact as 3 of the 4 RI tracks were removed. All that's left are 5 home signal levers, 1 point lever and one lock lever (210) to reserve the diamonds.
Here we see the tail end Charlies, levers 216 to 224.
Looking down the pistol grips lengthwise.
Quarter view of the interlocking frame from the stairwell showing the operator's lockers and the GRS Model 5 lever frame.
View along the top of the frame showing the glass panels. Unlike some other towers with Model 2 machienes there is ample space to walk behind the lever frame and in this case you can see the crew lockers and a variety of plants have been stored in this location.
Operator's desk with radio, phones and various forms and block sheets. To his right is a feet from one of the railroads' CTC system. Today UD tower is owned and operated by METRA giving their commuter trains priority over the diamonds and for boarding on the Alton tracks. METRA would also make sure to give priority to Amtrak trains which use the Alton Main as METRA must use Amtrak's Chicago Union Station and would not want to engender any bad blood.
Moving down into the relay room we find a real surprise as unlike the cramped dirty firetrap we saw at 16th St crossing, the UD relay room is clean, uncluttered and the relays appear to be arranged in taxidermy specimen cases like its some sort of museum!!
Same view taken from ground level. A few modern components have made it into the relay cases.
View of the relay cabinets from the opposite side.
View from the tower of two BNSF units #4351 and #1057 (4400hp GE model C44-9W's) running elephant style at the head of a westbound double stack intermodal train on the former ATSF main line.
We conclude with a photo of Joliet Union Station with a Metra commuter train laying over on the Rock Island platform and signals 62, 63 and 64 in the foreground. It appears that the 63 singleton signal was moved from its old post to a new, lower post on the center platform.
Next in this series is former Milwaukee Road Tower A-2 also known as Western Ave where its 3 track main line crosses the former Chicago Northwestern 4-track Western Main Line at grade.