Underground Pittsburgh: Explore our City of Tunnels

Delve below the surface to explore the underground areas that serve as vital pathways to our region.

Wabash Tunnel/photography by Chuck Beard and Renee Rosensteel


The Fort Pitt Bridge may be a Pittsburgh icon, but the double-decker span doesn’t function without the adjoining 3,600-feet-long holes through an abutting steep hill.
Neither do the Parkway East/Commercial Street Bridge in Squirrel Hill, the Liberty Bridge or the Panhandle Light-Rail Bridge, all linked to tunnels through which more than a quarter-million vehicles and who knows how many people pass each day.

Pittsburgh is the City of Tunnels as much as it is the City of Bridges.

Whether we’re headed to Mount Washington, Downtown or Pittsburgh International Airport, whether we’re traveling by car, train, transit or on foot, whether our destination is work, business or pleasure, we would be hard-pressed to get around these parts without depending on some type of tunnel.

We’ve got traffic tunnels and railroad tunnels, airport tunnels, transit tunnels, pedestrian tunnels, bicycle tunnels, a tunnel at times designated for high occupancy vehicles — even a tunnel for wildlife to pass under Interstate 376 without being smashed by cars.

Together, these active underground passageways constitute a network arguably as integral as bridges to mobility in western Pennsylvania. 

“They’re essentially out of sight, so we don’t think about tunnels as much as we do about bridges unless there’s a problem or construction,” says Pittsburgh Mayor Bill Peduto. “[But] a significant part of our city is underground, and those underground connections are vital to our success.”

The region is dotted with hand-dug tunnels, cut-and-cover tunnels, twin transit tunnels under the Allegheny River and a tunnel deep below a cemetery in Mt. Lebanon. The Fort Pitt Tunnel opens on the Downtown side to reveal an internationally acclaimed vista, prompting many newcomers to celebrate Pittsburgh’s “front door.” 

“So many tunnels and bridges make Pittsburgh unique,” says Dan Cessna, District 11 executive for the Pennsylvania Department of Transportation. “The combination of passing through the Fort Pitt Tunnel onto the Fort Pitt Bridge provides a dramatic ‘Pop!’ to reveal our famous view. If there were one without the other, the effect would not be the same.”

It’s not clear if engineers and architects deliberately wove the tunnel to the upper level of the double-decker bridge to create such a spectacular sight of the city, but if so,

“That person deserves an award,” says Peduto.

Train tunnels slice through the South Side and the heart of Oakland. Our region also is home to one of the nation’s longest vehicular tunnels, as well as curved tunnels and tunnels in the basement of the city’s tallest building, the U.S. Steel Tower.

We have abandoned tunnels, one-lane tunnels, repurposed tunnels, century-old tunnels and the vestige of a tunnel said to have served as part of the “Underground Railroad” in the era of slavery.

Close a major traffic tunnel, and the city is virtually paralyzed. Tens of thousands of vehicles are diverted, causing transportation mayhem in terrain dominated by hills, valleys and rivers.    

North Shore Connector


The American Association of State Highway and Transportation Officials defines tunnels as “enclosed roadways with vehicle access restricted to portals regardless of type of structure or method of construction,” but the definition pertains only to traffic tunnels. Under that standard, for example, the Federal Street underpass of I-279 on the North Side doesn’t count as a traffic tunnel although it’s longer than many that do.

While we could find no single, comprehensive listing of tunnels of all types — locally or nationally — we did come across scores of other tunnels around the region, especially south and east of Pittsburgh.

The busiest concentration sits above Carson Street in the city’s Station Square area — the Liberty and Fort Pitt tunnels for regular traffic, the Mount Washington Transit

Tunnel for buses and light-rail vehicles, and the Wabash Tunnel for HOV use (although its HOV restrictions have been lifted through August due to construction work on West Carson Street).

During a typical weekday morning rush hour, 120 buses and 84 light-rail vehicles carrying thousands of commuters squeeze past each other between 6 and 9 a.m. while sharing the narrow, 112-year-old Mount Washington Transit Tunnel. The Port Authority acquired it from the former Pittsburgh Railways Co., remodeled it and linked it to the South Busway in 1977 and later to a new South Hills T line.


Fort Pitt/Squirrel Hill Tunnels

These two tunnels serving the Parkway West and Parkway East can be likened to heart valves on Pittsburgh’s aorta of a highway.

In the morning, the tunnels restrict the flow of inbound traffic as motorists head for limited, tightly configured Downtown exits or simply try to fight through the mess to reach other destinations.

In the afternoon, the tunnels hold back drivers anxious to get out of town, turning what engineers sometimes call the “Parkway Central” into a 4-mile-long parking lot.

Consequently, traffic backs up predictably on the primary highway serving local and regional travel as I-376, the trunk of Pittsburgh’s arterial road network.

Allegheny County Executive Rich Fitzgerald suggested several years ago it might be time to start thinking about building another tunnel to provide relief for the Parkway West section that regularly ranks as one of the nation’s most congested.

For now, though, forget it. Pittsburgh’s notorious tunnel gateways aren’t about to change any time soon.

 “We have no grand plans to add new lanes or do anything dramatic,” Cessna says. “You’d have to completely revamp the Parkway East and Parkway West, which would be extremely difficult with the topography, the disruption, [proximity of] communities next to the highway and the magnitude of costs” that likely would exceed $1 billion.

​PennDOT has been engaged in sophisticated traffic studies based on maintaining the Fort Pitt and Squirrel Hill Tunnels as “fixed points,” with no major changes planned. The most likely change on the horizon involves reconfiguring the Banksville Interchange to minimize traffic weaves and yields west of the Fort Pitt Tunnel.

 “Our goal is to significantly improve the traffic flow,” Cessna says. “If you’re sitting at the top of Greentree Hill in rush hour, it should take you 30 percent less travel time” to reach the Downtown side.

Both tunnels, which were built to accommodate post-World War II suburban sprawl, are of similar design and operation. The Squirrel Hill Tunnel is 600 feet longer (4,225 feet) and opened seven years earlier (June 5, 1953).

In recent years, PennDOT has spent $84.9 million on life-extending repairs and upgrades ranging from removing tunnel roofs and lowering the Fort Pitt roadway to installing new ventilation systems and brighter lighting.

​PennDOT has been analyzing information to gauge the results of its work and money. Changes have greatly reduced problems involving over-height trucks.

Cessna says he already experiences faster driving times at the Squirrel Hill Tunnel during his daily commute to his office in Collier Township. “I don’t have evidence to support it but, anecdotally, traffic on the Parkway East has been moving more smoothly,” he says, partly because the Squirrel Hill Tunnel entrances appear visually bigger and less threatening, assuaging the tendency of approaching drivers to hit their brakes and slow down.

People affected in recent years by the extensive tunnel repairs and upgrades know the challenges of getting around despite PennDOT’s efforts to schedule construction-related closings and restrictions to the least inconvenient days and times.

Events beyond PennDOT’s control are more likely to disrupt things.

The latest records show 81 “reportable accidents” in the Fort Pitt Tunnel and 143 in the Squirrel Hill Tunnel from 2011 through 2014. “Fender-benders” aren’t counted.

More than 2,700 other “tunnel incidents” a year in those two tunnels over the same four-year period have caused far more, albeit shorter, delays — disabled vehicles, abandoned vehicles, pedestrian encounters, debris clean-ups, weather issues and miscellaneous other interruptions.

Such emergency responses keep 68 employees assigned 24/7 to maintain PennDOT’s three biggest tunnels on their toes.

 “We get more ‘Thank-yous’ from people being assisted [in tunnels] than any other facet of our work,” Cessna says. “Our people take great pride in the special service they provide.”


Liberty Tunnel

For a period during World War II, motorists who used the Liberty Tunnel were required to “share the road” — not with bicycles but with horse-drawn wagons.

A ban on horses trotting through the 1.1-mile-long tubes was lifted when gasoline was rationed during World War II as part of the American war effort. Small business owners once again could move goods in the same old-fashioned way as others did during the first eight years of the tunnel’s existence.

Horse-drawn wagons mixed among motor vehicles are a small part of the storied history of the oldest traffic tunnel in Pittsburgh, now closing in on a century of linking the South Hills, South Side and Downtown (once the Liberty Bridge opened in 1928) instead of requiring drivers to skirt around Mount Washington via its West End gap.

On average, 65,000 vehicles a day use what was the longest automobile tunnel in the world when it opened March 23, 1924.

Liberty Tunnel ventilation Exhaust Fan


Less than two months later, dangerous levels of engine exhaust triggered an emergency that left drivers and rescuers overcome by carbon monoxide. Twenty-one people required hospital treatment; fortunately, no one died. In the aftermath, police restricted the number of vehicles entering until a ventilation system was completed.

The Liberty Tunnel has never been Pittsburgh’s best-looking or best-performing “hole in the wall.” To wit: Poor lighting for decades, stop-and-go traffic during rush hours, congestion at both ends and water stains as a result of wall cracks and leaks due to age.

Cessna described the tunnel several years ago as Mount Washington’s “old faithful.” His PennDOT team recently completed seven years and $46 million worth of phased repairs and upgrades to bring function, safety and appearance to more modern standards.

Eight 12-foot-diameter fans, each operated by 250-horsepower motors, uniquely ventilate the tunnel. The system can maintain a 15-mph air flow through each of the parallel tubes, using vents to pull out exhaust and introduce fresh air.

Ventilation shafts 200-feet high connect to a brick “fan house” on Secane Street atop Mount Washington, where four tall stacks disperse the fumes. The building will be preserved as a historic landmark, but equipment will be replaced and modern computer controls will be installed as part of an upcoming $22 million PennDOT project.

Allegheny County owned the Liberty Tunnel until PennDOT’s predecessor, the Pennsylvania Department of Highways, took it over in 1962.

Liberty Tunnel emergency passage


Did you know?

the ‘Liberty Tubes’
The name “Liberty” was selected as a symbol of hope for lasting world peace after the Allied victory in World War I.

A jail cell built at the north end in 1938 housed “any law violators caught in the tubes, or escaping over the Liberty Bridge, until a patrol wagon can be sent around to cart them off to jail,” according to the Pittsburgh Post-Gazette.

Emergency passages every 500 feet connect the inbound and outbound tunnels, providing escape in case of fire, smoke or other unsafe situations.

The tunnel to accommodate the emerging “Automobile Age” cost $6 million to build and involved excavating 400,000 cubic yards of earth and rock over five years. Crews hauled the debris a short distance south on Saw Mill Run Boulevard to create the city’s McKinley Park.

Public debates preceding construction included a proposal to cut through Mount Washington instead of building a tunnel.

For decades, police perched in small, elevated booths manually controlled rush-hour traffic signals at both portals.

As part of a 1975 overhaul, antenna wires were strung the length of tunnel roofs, enabling motorists to get AM radio reception.

Cleaning the Liberty Tubes
While the city sleeps, PennDOT scrubs the walls of three major tunnels – Squirrel Hill, Liberty and Fort Pitt. A “wash crew” supervisor and three workers do their thing overnight when traffic is light, using a pickup truck, a “crash truck” for safety and a custom-built “wash truck” equipped with brushes and carrying a soap solution. It’s a $400,000-a-year expense. The crew puts the wash cycle on hold in winter when temperatures drop below freezing.


Next: More Pittsburgh Tunnels



Armstrong Tunnel

Lore says the twin bores under “The Bluff” bend in the middle because of a mistake that shamed the project engineer into killing himself. Not true. Actually, the tunnel was so designed to align with streets at both ends and because of geological factors.

Built in 1926-27, the western side is the only major tunnel in Pittsburgh with an active walkway despite the lack of mechanical ventilation. Natural air drafts flow toward the Monongahela River, and they’re sometimes strong enough to enable bike riders to coast from Forbes Avenue to Second Avenue.


Wabash Tunnel

If any tunnel is a misfit, this is it: Anyone remember Skybus? This former railroad tunnel — its north portal sits at the base of Mount Washington across from Station Square — was fitted with a concrete guideway in the early 1960s for a proposed automated, rubber-tired transit system that met political death before its construction.

The Port Authority then used the Wabash Tunnel to store old buses until vandals crept in and broke the bus windows. The Port Authority razed the guideway to accommodate a proposed South Busway extension and a connecting Mon River transit/pedestrian bridge, which was never built.

The Wabash finally reopened in 2004 as a “mixed-use facility.” While the Port Authority owns the reversible, sparsely used HOV tunnel, not a single bus uses it. Built in 1903, the Wabash enabled trains to travel Downtown for 40 years. Stone piers from the long-demolished railroad bridge still stand in the Mon River.


South Side Works Tunnel

Many people delight in watching CSX freight trains roll along the busy tracks hugging the Monongahela River next to Station Square. But if you’ve visited the Hofbrauhaus, Cheesecake Factory or Hyatt House at SouthSide Works, did you ever wonder, “Where did they go?”

Shhhh! You may hear the trains a comin’ beneath you in a shallow tunnel between South 25th and Hot Metal streets. The tunnel, meant to bypass activity at the now-defunct LTV Steel Works, runs under Tunnel Park in the city’s popular retail-business-entertainment redevelopment.


“Green Man’ Tunnel”

The abandoned, 175-foot-long Piney Fork railroad tunnel in South Park Township is a source of urban legend, supposedly haunted by the ghost of Raymond Robinson, who survived severe electrocution from high-voltage trolley lines near Beaver Falls as an 8-year-old boy.

He lost his eyes, nose, an ear and an arm but lived until age 74, going out only at night to avoid stares. People sought him out as he walked, using a stick to find his way. Some took photos with Robinson, who they described as friendly. He became known as the “Green Man” because infections left his skin green-tinted and as “Charlie No-Face” because of his disfigurement. It is said his ghost now spooks other tunnels besides the Piney Fork tunnel. Who knows where the Green Man lurks?

While pranksters costumed in “Green Man” spandex bodysuits occasionally pop up in public, PennDOT has introduced a Running Green Man symbol in the Squirrel Hill and Fort Pitt Tunnels. He’s coming soon to the Liberty tunnels. In an emergency, the figures on tunnel walls indicate the direction people should travel to reach the nearest escape passageways.


Green Tree Tunnel

The nearly mile-long train tunnel runs under Green Tree Borough. Built by the one-time Wabash-Pittsburg (Yep, without the “h.”) Terminal Railroad, it is owned by the Wheeling & Lake Erie Railroad and is still in service.

The 1903 tunnel begins at a rail siding known as “Rook Yard,” part of a small industrial complex off the Parkway West. It passes under a half-dozen residential streets before emerging in the east at Alcon Street and Greentree Road. The trestle crossing the Parkway West at the bottom of Greentree Hill is part of the W&LE RR line.


North Shore Connector

Twin 22-foot-diameter tunnels under the Allegheny River are the only tunnels in the region that pass under water. They were bored in 2007-2009 by a worm-like, 500-ton machine brought from Germany. When you’re riding the T between Downtown and the North Shore, you’re riding on tracks that descend to a maximum depth of 65 feet below the river surface, protected by 11-inch-thick concrete tunnel shells. The best part? The T is free between Downtown and the North Shore.

The city’s “underground” houses significant public art. A special Romare Bearden tile mural, “Pittsburgh Recollections,” lives on at the Port Authority’s Gateway T Station. The mezzanine at the Wood Street T Station features Sol Lewitt’s slate-on-marble “Thirteen Geometric Figures.” Hand-pressed glass blocks backlit in neon colors (pictured) highlight Steel Plaza T Station. Colorful mosaics line a pedestrian tunnel at the U.S. Steel Tower.


Mount Washington Transit Tunnel

The one-time coal-mine-turned-tunnel was upgraded in 1904 and used by as many as 600 streetcars a day at its peak. The 6 percent grade in the 3,500-foot-long tunnel is one of the region’s steepest.

On Christmas Eve in 1917, a streetcar ran out of control and overturned on Carson Street, killing 21 people and injuring 80. The disaster resulted in civil lawsuits that led to the first of several Pittsburgh Railways Co. bankruptcies.

Another significant crash occurred Oct. 28, 1987, when an inbound Port Authority streetcar lost power and brakes, failed to make the right turn at the end of the tunnel, sideswiped a bus and car, veered across Carson Street and crashed into a Station Square office building. Forty passengers were injured — none seriously.


Pittsburgh International Airport

Two parallel, 2,600-foot-long tunnels house the familiar people movers used to shuttle millions of passengers a year between the Airside and Landside terminals. The airport has three other, seldom-seen tunnels beneath the tarmac — an emergency evacuation tunnel between the two people-mover tunnels, plus a baggage system tunnel and a utility/freight/service tunnel nearby


Downtown Connections

While the subway bisects the Golden Triangle, only one station — Steel Plaza — provides underground connections to nearby streets and buildings. Special walkways serve the U.S. Steel Tower, BNY Mellon Center and BNY Mellon’s Client Services Center on Ross Street.

A larger cluster of pedestrian tunnels also can be found at Gateway Center-Equitable Plaza with access to the Wyndham Grand Pittsburgh Downtown Hotel, the Stanwix Parking Garage and four office buildings.

When the subway was being planned, building owners in proximity to the Gateway Center “T” station were approached about providing underground connections. They said no. Passageways connecting city and county buildings at Grant Street have been closed for security reasons since the 9/11 terrorist attacks.


“Underground Railroad” Tunnel

Designed to provide secret passage to a “safe house” for slaves during the Civil War, the tunnel was built by a German immigrant between 1860 and 1862 at what is now the history-steeped Morning Glory Inn, a bed-and-breakfast on the South Side.

The low, narrow, brick-lined tunnel is 15 feet long, extending from the basement and under a sidewalk to an 8-by-24-feet brick-walled room under part of Sarah Street. While it’s not known definitively if the tunnel ever provided a safe haven for slaves, the inn’s website notes that it may have seen “very heavy use” later to smuggle booze during Prohibition.


Schenley Tunnel

Also known as the Neville Street Tunnel, it runs a half-mile through the heart of Oakland, out of sight and out of mind, about 70 feet below and following the Neville Street alignment between Centre Avenue and Filmore Street near Carnegie Mellon University.

CSX owns the line used mostly by the short-line Allegheny RR and by Amtrak for Capitol Limited train passenger service to Washington, D.C. City officials now salivate over the corridor’s possible future use for transit linking Oakland and the new Almono development site in Hazelwood.


​Enlow Tunnel

Unless you’re into biking and hiking, you’re not likely to experience this lighted, 558-foot-long former railroad tunnel in Findlay Township that now is part of the Montour Trail.

While the old Montour RR tracks were still in place in 1981, former Allegheny County Commissioner Dr. William Hunt took 400 passengers on a circuitous train ride over existing rails from the city and eventually through the Enlow Tunnel to a siding near Pittsburgh International Airport. He intended to demonstrate the potential for commuter rail. To his guests, the trip seemed to take forever. It was the last trip ever.


Layton Tunnel

Off the beaten path, this one-lane, spooky railroad tunnel in a rural area near Perryopolis, Fayette County, connects to a shaky, one-lane, railroad bridge over the Youghiogheny River that is listed on the U.S. National Register of Historic Places. Drivers must look through the equivalent of the length of a football field to see light at the end of the tunnel — no kidding — and make certain there’s no oncoming traffic before proceeding. Courtesy generally prevails. The tunnel-bridge combo dating back to 1899 leads to an Allegheny Passage rail-trail access point, a canoe-kayak rental business, a house in the tiny village of Layton where a scene was filmed for the movie “Silence of the Lambs” [For more on the making of this film, see Rick Sebak’s “All Roads …” column on page 23] and the United Steelworkers Union’s Linden Hall Resort several miles away.  

Tunnels by the Numbers

$6 million
What PennDOT spends per year to maintain the Fort Pitt, Squirrel Hill and Liberty tunnels, including salaries, maintenance, emergency response, tunnel-washing and keeping crew-cab trucks and tow-trucks at all three locations.

Number of lights installed in the latest upgrade of the Liberty Tunnel.

Number of fatalities in Fort Pitt and Squirrel Hill tunnel accidents, based on PennDOT records dating back to 1997.

Number of fatalities in the Liberty Tunnel over the same period.

Known number of births inside the Liberty Tunnel. In January 1999, a woman in labor and her husband were on their way to a hospital when a pothole flattened a tire on their car. When they exited the tunnel, they were the parents of a healthy infant boy.

Average daily light-rail riders using Downtown subway and/or North Shore Connector tunnel.

Average daily traffic through the Fort Pitt Tunnel, Pittsburgh’s busiest (by volume). The Squirrel Hill Tunnel is second, with 94,700 vehicles, followed by the Liberty Tunnel, with 65,000.

Amount PennDOT has spent on Fort Pitt, Squirrel Hill and Liberty tunnels projects over the past 15 years (most of it over the past seven years).

Length in feet of the Sideling Hill Tunnel, longest in the state until the Pennsylvania Turnpike abandoned it in 1968 and shifted traffic to a mountain bypass. It is slated to be restored as part of a “Pike2Bike” project.

Approximate number of nights a year PennDOT crews spend washing Pittsburgh’s three major tunnels.

Joe Grata covered the transportation beat for nearly four decades for The Pittsburgh Press and later the Pittsburgh Post-Gazette, reporting on highways, bridges, transit, funding, safety and related issues of local, state and national significance.

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