Pittsburgh's light rail system is descended from PCC-based streetcar lines running south of the city that had the good fortune to have both their own rights of way and the use of a dedicated tunnel through Mount Washington. These advantages earned the system a light rail style conversion in the 1980's complete with a downtown subway and dedicated bridge across the Monongahela River. While the rebranded Mount Washington Transit Tunnel continued to underpin the network, the Allegheny Port Authority and its predecessors had recognized the Mount Washington Tunnel as a single point of failure and therefore maintained an alternate surface route up and over the hill. Christened the 52 Allentown in 1984, this alternate route, terminating at South Hill Jct, would see declining levels of service until it was discontinued entirely in 2010. However tunnel diversions kept the old 52 Allentown in service as a ghost line, light rail trains running doors closed through the eponymous neighborhood on an as-needed basis. For out of town railfans catching a ride over the 52 was particularly difficult as the diversions were not often scheduled in advance, however in 2025 the tunnel was to undergo a long term renovation with Route 47 and 42 trains diverted over the 52 for the better part of a year. This allowed me to schedule a trip to Pittsburgh to get photos and videos of this rare occurrence.
My arrival in Pittsburgh was too late in the day to properly ride the 52 Allentown, but I was able to catch the arrival of westbound Amtrak Pennsylvanian Train 43 with P42DC leading the usual consist.
It was at this point I had my first ever encounter with a Rule 280a "Clear to Next Interlocking" signal indication displayed eastbound on Track #1 at the former CP-EAST PITT. Displayed as a flashing white marker light next to a standard Medium Clear, the signal us used in cab signal territory without wayside intermediate signals for train movements that are not cab signal equipped. In this case said movement would be Train 43 shoving back to CP-HOME where the turning wye is located.
By displaying Rule 280a instead of a Restricting, the shove move would be able to operate at speeds up to 45mph, saving considerable time across the 8 mile round trip.
The following morning I caught a light rail train at Steel Plaza and was in place to get photos as it crossed over at Panhandle Interlocking and onto the short single track that would lead to the street running up and over Mt. Washington via Allentown.
The whole trip takes about 8-10 minutes, about 5 minutes longer than the trip through the tunnel. The ride was downright exciting as my LRV's operator was really flooring it up the twisty grade. A temporary infill station was also added along the route in the Allentown neighborhood.
My outbound SD400 LRV, running on a 47S service, at South Hills Jct
South Hills Jct is built around a large double track scissors crossover. Although from the point of view of the platforms the crossing routes over the diamonds are in a geometrically straight path, from a railroad interlocking point of view those would be the diverging routes. Normally the light rail trains get a solid yellow lamp for a Restricting indication into street running track. However for the "diverging" route, they get a flashing yellow.
In its original configuration trains from the Overbrook and Beechview lines would merge into the transit tunnel with the option to use the 52 Allentown Route.. With Overbrook Line trains making use of a new flying junction since 2004 and the 52 being discontinued in 2010, the scissors crossover sees rather limited use in its role as a crossover. Here SD400 LRV #4221 crosses northbound over from the Beechview Line to the 52 Allentown line.
Pride month pay have been over, but SD400 pride unit #4239 was still roaming across the light rail system in early July, along with 4202.
Here we see SD400s #4227 and #4201 along with CAF LRV #4317 running out of the junction and up the incline towards Allentown.
CAF LRV #4315 descending southward from the Allentown route. The CAF LRVs were a supplemental order of vehicles to support the re-opening of the Overbrook line, which was closed between 1993 and 2004.
Like the northbound trains, southbounds would roll towards the junction and get a Restricted Diverge flashing yellow signal on the dwarf.
View along the axis of the scissors crossover route from the Beechview/Overbrook lines to the Allentown Line with CAF LRV #4317 and SD400 #4253.. While this routing is physically straight, as far as the interlocking is concerned this a diverging route.
In this video we see an inbound 42S South Hills Village (via Beechview) train with SD400 LRV's #4231 and #4235 passing an outbound 42S with CAF LRV's #4310 and #4313 with #4310 sporting the new "Pittsburgh Regional Transit" paint scheme.
In my previous visit to South Hills Junction in 2023, both PCC loops were still present for short turns both from the north and south. Since that time the southward loop for PCC's coming off the 52 Allentown has been removed along with its boarding platform. PCC's were used through 1993 as the old Overbrook line had wooden trestles that could not support the weight of LRVs.
On the other hand, the old Route 47/52 platform had been re-paved. Before the Overbrook Line rebuild this platform had served the PCC's using the 47 route as well as all 52 Allentown cars which terminated at South Hills Jct.
Another view of LRV's crossing over to the Route 52 with SD400 #4250 and CAF LRV #4308.
The tunnel closing also affected local bus traffic which also had to detour up and over Mt Washington. Here bus #6236 passes inbound SD400 #4227.
All of the construction miscellany made getting a view into the tunnel a bit difficult, but I was able to manage a photo.
Back to the South Hills Jct platforms where I caught SD400 #4224 passing #4201 and #4206 arriving southbound.
The return trip was not quite as exciting, I'm guessing the operators know they have a bit more leeway for speed on the steep ascent since the grade will quickly bring the car to a stop without use of brakes.
Heading north across the Panhandle Bridge I encountered CAF LRV #4314 painted in the new "Pittsburgh Rapid Transit" branding.
Final photo of this set if SD400 #4224 after dropping me off at the Honorable United States Steel Plaza.
All in all Pittsburgh Light Rail is a great little system that still presents a lot of heritage due to the early date of its light rail conversion. If the MWTT ever shuts down again I urge you all to schedule a visit.
During some recent trips through Pittsburgh I have had the opportunity to revisit the Port Authority Transit light rail that runs southward from the downtown triangle. In 2022 I made my first trip out to South Hills Village, with intermediate stops at Washington and Overbrook Junctions. For this year, while the 47L out to Library seemed tempting, the hour long trip time in each direction would exceed my time budget so I looked for something a bit closer to downtown. The obvious answer was to spend some time at South Hills Junction, located on the other side of the Mt Washington Transit Tunnel. So while I didn't go very far in distance I was able to explore one of the most interesting and iconic parts of the system. You can find the full gallery here ( mirror ).
As my visit involved an overnight stay I got this night photo of Pittsburgh Penn Station shrouded in the haze of wildfire spoke that had blown down from Canada. This haze would continue to impact my photos on the following morning's trip.
Heading out to South Hills Jct I pass Siemens SD-400 #4247 at the First Ave station. First Ave was built as an infill station to serve the south side of downtown which had seen increased development since the downtown light rail tunnel was opened in the mid 1980's. Part of this development was on the former site of the B&O Railroad station. First Ave also marks the boundary of the fare free downtown transit zone.
CAF LRV #4313 pulls out of South Hills Jct on a 42S Beechview Line run to South Hills Village. It is at this point where trains bound for the Overbrook line take the right hand diverging route onto the flyover.
PAT operates two batches of equipment, 55 SD-400 LRV's that entered service in 1985 and another 38 CAF SD-400 copies that came on board in 2003 for the restoration of the Overbrook Line. Apart from the numbers, the easiest way to tell the two classes apart is the design and placement of the center mounted headlamp. Below we see CAF LRV #4309 and SD-400 LRV's #4204 and #4230 departing South Hills Junction station towards Pittsburgh.
A week before my visit, Pittsburgh had hosted the American Public Transport Association (APTA) conference and had wrapped SD-400 #4202 for the occasion.
The Junction in "South Hills Junction" comes in the form of a double scissors crossover that connects on one side the Overbrook and Beechview Lines with the Allentown Line and Mt. Washington Tunnel on the other.
When built the service patterns made full use of the junction, but today it is essentially straight railed between the Mt Washington tunnel and the high level Beechview Line platforms as seen here with CAF LRV #4326.
Although a tower-like building is present, it is not clear if it is, or ever was, staffed for the purpose of routing trains through the junction. This is because the light rail system is equipped with automatic route setting transponders as seen under #4207. After LRV's berth at the platform, the route is lined and a Restricting signal displayed on the attendant dwarf signal.
The seemingly abandoned low level platforms at South Hills Jct are a remnant of the original Route 47 Overbrook line that bypassed the extensive street running on the 42 Beechview Line with a dedicated right of way that ran direct to Overbrook Junction. Modernization of the Overbrook line was deferred due to the cost of replacing large segments of single track and several rickety wooden trestles that could only support the weight of PCC cars. Routes 47 service was abruptly suspended in 1993 when the condition of the trestles became a safety hazard with rebuilt efforts beginning in 1999 and finishing in 2004. The "modern" LRV quality line would split/join with the Beechview via a brand new flying junction south of rebuilt high level platforms. The low level platforms would continue to see use as the terminal of the 52 Allentown, until that service was indefinitely suspended in 2011 due to recession era austerity cuts.
Despite all the times I visit Pittsburgh, until 2022 I had yet to ride all of its light rail system. Built before World War 2 to support its vast streetcar network, the Pittsburgh LightRail system consists of two main routes that head south of the city using the Mount Washington Transit Tunnel. The 42 is mostly surface running along Broadway Ave in Beechview and Dormont. The other route, 47, was half rebuilt as a "modern" light rail line in the 1990's, largely replacing the last of the PCC's, with the outer half retaining its PCC era configuration to this day. I had ridden both these trunk lines, as well as the now discontinued 52, around 2010. However due to the quirks of the old school Allegheny County Port Authority Transit (PAT) fare system, I never rode the short bit of the 42 between Washington Junction, where the 47L splits off to Library, and South Hill Village. A decade of time and one updated fare system later I found myself back in Pittsburgh without any railroad signaling related missions on my plate so it was finally time to complete the Pittsburgh Light Rail system by going to South Hills Village. You can find the full gallery here ( mirror ).
My journey begins at Wood St station in Pittsburgh's Light Rail Subway that runs from the north side of the Allegheny River and through downtown. Here a Siemens SD400 type LRV passes through the crossover south of the station. My outbound trip would be provided by LRV #4327.
In the mid-1980's PAT made use of the old PRR Panhandle Route west of Pennsylvania Station to replace its downtown street trackage with a trolley tunnel. The Panhandle Route connected Pittsburgh to Chicago via Columbus and Logansport as opposed to the northerly route via Fort Wayne and exited Penn Station via a tunnel under downtown that would form the nucleus of the current PAT light rail subway. Here we see PAT LRV #4325 on a 47L routing heading inbound at the 1st Ave station. 1st Ave was an infill station built in the early 2000's to in part serve the redeveloped footprint of the former B&O a href="https://en.wikipedia.org/wiki/Grant_Street_Station">Grant Street Station.
The Panhandle Bridge was built for the PRR's Panhandle Route and could support all manner of heavy main line railroad trains. Today the steel truss bridge is barely breaking a sweat with the LRV's that now cross it. Reuse of the disused railroad infrastructure allowed the Smithfield St Bridge used by the PCC's exiting the transit tunnel, to be rebuilt in 1994-95.
PAT Siemens SD400 LRV #4249 at Station Square. PAT received two batches of SD400 pattern high floor LRV's. The first 55 were built by Siemens in the mid-80's to go along with the downtown tunnel project. A second order of 28, numbered in the 4300 series, was built under license by CAF in 2003-4. Travel in the downtown part of the system was historically free with Station Square being the first point that would trigger a fare. This arrangement made trains pay as you enter towards downtown and pay as you exit heading away from downtown.
The Mount Washington Transit Tunnel, along with the large amount of dedicated right of way, is what prevented full bustitution of the Pittsburgh light rail system. Built in 1902, the 3,500 foot tunnel was necessary to get streetcars past the imposing Mouth Washington on the south bank of the Monongahela River. The southern end of the tunnel empties out into South Hills Jct where the routes 42, 47 and 52 all meet.
Also known as the Overbrook Line, the Route 47 ran on a dedicated right of way between South Hills Jct and Overbrook Jct. Although it was a completely dedicated right of way, it was built to classic streetcar/interurban standards with a single track, short passing sidings and wooden trestles over the rivers and roads of the valley. Not rebuilt in the first wave that brought in the LRV's, the 47 saw PCC operation until 1993 when the shut the whole thing down due to poor structural integrity of the trestles. The line would not reopen until 2004 having been completely rebuilt to modern light rail standards with cab signaling, double track and full high level boarding. Below is Boggs station, just past the point where new flyover ramps were built to join the Route 42, replacing the original alignment that used the at-grade crossovers at South Hills Jct.
CAF built SD400 #4301 near Boggs. The 2004 28 car supplementary order was to ultimately replace the Overbrook Line PCCs that were retired without replacement in 1993.
SD400 #4252 near Killarney. Despite being modern, the new Route 47 has little of the charm of the classic Route 47.
Overbrook Jct is where the Routes 42 and 47 merge into a single trunk line. Between 1993 and 2004 all light rail traffic would diverge to the left down the Route 42.
