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90.5 WESA's Good Question! series is an experiment where you bring us questions—and we go out to investigate and find answers.So: What have you always wondered about Pittsburgh? Are you curious how your neighborhood originally received its name? Or maybe why the Mon and Allegheny Rivers are different colors when they merge at the Point? Or maybe you've always wanted to know what happened to all of our street cars and inclines? From serious to silly, we're here to help.

Over The River And Through The Hills: Everything You Never Knew About Pittsburgh's Iconic Tunnels

Katie Blackley
90.5 WESA
Outside the Ft. Pitt, which was opened in 1960. The tunnels were built to accommodate Pittsburgh's growing suburban population.

Pittsburgh’s tunnels are considered the gateway to the city. More than 229,000 people drive through the Liberty, Fort Pitt, Squirrel Hill and Stowe tunnels each day.

This is part of our Good Question! series where we investigate what you've always wondered about Pittsburgh, its people and its culture.

PennDOT owns these four tunnels. Three of their experts answered questions from 90.5 WESA listeners for our GoodQuestion! series about these essential pieces of infrastructure and shared what they know about the history, operations and quirks of the passageways.

Credit Katie Blackley / 90.5 WESA
90.5 WESA
PennDOT operates the Stowe, Liberty, Squirrel Hill and Ft. Pitt Tunnels. Allegheny County owns the Wabash Tunnel and the City of Pittsburgh maintains the Armstrong Tunnel.

What occupies the space above the Squirrel Hill tunnel? – Kathy Stec

Credit Katie Blackley / 90.5 WESA
90.5 WESA
Above the Squirrel Hill and Ft. Pitt Tunnels are rooms with large windows so engineers could monitor traffic and check conditions. Now, most of the work is done remotely.

When the Squirrel Hill tunnel first opened in 1953, engineers didn’t have computers and cameras set up throughout the tunnels. Instead, they monitored traffic and operations by watching it happen.

According to Ben DeVore, PennDOT’s tunnel maintenance manager, workers could change traffic patterns or shut down the tunnel completely from the space above the tunnel. Now, he said, it’s mostly a storage space, but still functional.

“All of the electrical and mechanical equipment for the tunnel (is there),” DeVore said. “There is some office space, as well.”

A few years ago, Bob Hazen from WTAE-TV walked through the building above the tunnel and tweeted pictures of the rooms and old computers.

Why does the Liberty Bridge not connect to the Liberty Tunnel perfectly? – Maureen Kennedy Macel

This one stumped PennDOT’s crew. Engineer Bill Lester guessed the alignment might have to do with what used to be at the city-side mouth of the tunnel.

”When the bridge wasn’t there, it was actually a roundabout,” Lester said. “Everything either went up McArdle Roadway or down McArdle Roadway into South Side or up to Mt. Washington.”

Credit Google
The intersection of the Liberty Bridge and PJ McArdle Roadway once used to be a roundabout, with a monument in the center.

DeVore said the roundabout theory, coupled with PennDOT’s “right-of-way acquisition” might be the answer. Right-of-way acquisition is when the state of Pennsylvania takes over land for public transportation purposes. For highways, the width can range from 33 feet to more than 120 feet. He said this could have contributed to the road’s positioning. 

“But there’s no way to know for sure,” Devore added.

Who exactly designed and built the Squirrel Hill tunnel and interchange? - Chad Grosso

Construction on the Squirrel Hill tunnel began in 1946 and opened to traffic in 1953. It was designed by engineer Michael Baker, who also did the Fort Pitt tunnel. It’s a twin-tube tunnel and actually three separate structures: the “cut and cover” tunnel, the bored tunnel and what PennDOT calls “the catacombs.”

“Cut and cover means they opened up the earth,” DeVore said. “Then they built the tunnel and covered it back over. Then the other portion of it was bored the majority of the way.”

In 2000, a group of Carnegie Mellon University students and an electrical engineering professor installed wires throughout the tunnel to re-amplify radio waves. DeVore said by next year, all the tunnels will be able to pick up AM-FM frequencies, as well as cell phone reception.

Fast Facts:

- Lined up, the tunnels would reach 14,228 feet. Liberty is the longest, at 5,889 feet. 

- The Squirrel Hill tunnel sees the most traffic, with 101,635 commuters passing through daily.

- There used to be an “inebriation holding cell,” on the city-side of Liberty.

Credit Katie Blackley / 90.5 WESA
90.5 WESA
These "tunnel wreckers" once cleaned the tunnels.

“(If) anybody got rowdy downtown, they arrested you and they’d throw you in that drunk tank,” Robertson said. “Once the morning came through, they’d let the people out when they were sober.”

- PennDOT is installing LED lights in all of the tunnels, which can be adjusted depending on the light outside. This helps drivers’ eyes as they enter a tunnel, ideally keeping traffic moving.  

More than just a Tunnel

A nurse was once on call 24/7 at the Fort Pitt tunnel.

“If any employees got overcome with carbon monoxide, felt bad, or whatever, they would go down to the nurse’s station on the north end,” Lester said. “She had her own little hospital there.”

Robertson said each of the tunnel’s facades serve as reminders of the region’s economic situation.

“If you look at the Squirrel Hill Tunnel, it was built right after the war and everything was still pretty conservative, nobody was spending any money. So the facades are made of sandstone," Robertson said. “But if you come down the front of [Fort Pitt], it’s all marble. At that point the county was flush and things were good.”

In 2014, workers found a dog in the Fort Pitt Tunnel. His name was Chico and he was returned to his owner (he’d been lost for a few weeks).

When the Liberty Tunnel opened in 1924, horse and buggy was still a common method of transportation. DeVore said before the ventilation system was put in place, the horses, and sometimes their owners, would collapse trying to pass through. Even after the air shafts were drilled, horses were moving too slowly to keep up with their vehicular counterparts.

“They had to watch out so they didn’t get too many horses in there,” Devore said. “Because it would stall traffic out tremendously. They eventually did outlaw horses in the early 1940s.”

Stowe Tunnel in Stowe Township is the oldest of the PennDOT-owned tunnels. It was built in 1909 and runs about 500 feet. 

A baby was born in the Fort Pitt Tunnel in the 1990s.

Credit Katie Blackley / 90.5 WESA
90.5 WESA
PennDOT Tunnel Maintenance Manager Ben DeVore flips through archival documents at offices above the Ft. Pitt Tunnel.

“Mother wasn’t going to make it to the hospital,” DeVore said. “So they just stopped and that baby was born in the inbound tunnel.”

The little green running man signs are for emergency evacuation situations. They don’t, according to PennDOT, lead to a tunnel down the middle, just to the other side of the tunnels.

And inside the Liberty Tunnel is a safe that used to hold Allegheny County workers' payroll.

“So on pay day, all the employees showed up and lined up on Secane Avenue and collected their pay,” DeVore said.  

90.5 WESA’s Good Question! series receives a lot of submissions regarding Pittsburgh’s tunnels. This story includes the four PennDOT-owned tunnels, which do not include Wabash or Armstrong. PennDOT also doesn’t speak to the psychology of drivers going in and out of the tunnel. But if you’re looking for a great summation of why people slow down, check out this piece by The Incline editor Sarah Anne Hughes.

Back in 2015, 90.5 WESA's Margaret J. Krauss did a profile of the Liberty Tunnel ventilation system.

Also, WQED's Rick Sebak did a "It's Pittsburgh And A Lot Of Other Stuff" about the Squirrel Hill Tunnels:

What have you always wondered about the Pittsburgh region? Submit to our Good Question! series and we’ll go investigate and find answers.