A bridge doesn't usually move sideways.

But over the course of two days, that's exactly what happened outside Pittsburgh, where engineers completed one of Pennsylvania's largest-ever lateral bridge slides and moved a brand-new Interstate 376 bridge into place.

The operation is already paying off.

Following the successful installation, the Pennsylvania Department of Transportation (PennDOT) announced that I-376 Parkway East is now expected to reopen ahead of its original Aug. 3 target, weather permitting.

The milestone is part of the $95 million Commercial Street Bridge replacement project, one of the largest bridge replacement efforts of its kind in Pennsylvania.

Building first, moving later

Rather than rebuilding the bridge directly over one of western Pennsylvania's busiest highways, crews took a different approach.

They constructed the new bridge beside the existing one, allowing traffic to continue using the old structure for much of the project. Once the aging bridge had reached the end of its service life, crews demolished it and shifted the replacement into its permanent location using Accelerated Bridge Construction (ABC) techniques.

The slide began around 10 a.m. on July 19.

Using a specialized hydraulic skidding system, crews pushed the massive bridge 96 feet in about seven hours before completing the final six feet the following morning. Altogether, the structure traveled 102 feet into its final position.

The move relied on 42 independently operated skid shoes and integrated hydraulic jacks that lifted the bridge off temporary supports before carefully lowering it onto its permanent bearings.

PennDOT Secretary Mike Carroll said the innovative construction method dramatically reduced the amount of time drivers would have been affected.

"The innovation used in this project presented some unique challenges that our team was excited to take on, and it reduced years of public traffic impacts into a couple of weeks," Carroll said. "I am pleased to say with the help of our industry partners, the Commercial Street demolition and slide was a big success."

First came the implosion

Before the new bridge could take its place, the old one had to come down.

Crews used a controlled implosion at approximately 8 a.m. on July 16 to demolish the original Commercial Street Bridge. Over the following days, workers removed the remaining debris, prepared the site and readied the bridge for its historic sideways journey.

To make the work possible, Interstate 376 closed to traffic on July 10. Thanks to the project's rapid progress, PennDOT now expects the highway to reopen ahead of schedule. The exact reopening date will depend on weather conditions.

Commercial Street and the Nine Mile Run Trail are also expected to reopen shortly afterward.

"This bridge replacement has been going remarkably well and it's all because of the great collaboration and hard work from the many people helping move the project forward," said PennDOT District 11 Executive Jason Zang. "This great progress makes reopening the bridge to traffic ahead of schedule a strong possibility."

Why this bridge matters

The Commercial Street Bridge carries Interstate 376 between the Edgewood/Swissvale interchange and the Squirrel Hill Tunnel, serving one of the busiest corridors in the Pittsburgh region.

On an average day, about 100,000 vehicles travel across the bridge.

Construction on the replacement project began in June 2024 with reconstruction of the westbound I-376 off-ramp to Forest Hills/Wilkinsburg (Exit 78B). Since then, crews have installed temporary and permanent foundations, built piers and abutments, erected structural steel and completed phased intelligent transportation system work. To reduce disruptions, Commercial Street and the Nine Mile Run Trail were temporarily relocated while much of the construction took place.

The overall project remains on track for completion in summer 2027.

Keeping drivers informed

PennDOT is streaming a live camera of the bridge site so the public can watch the project's progress from a safe distance. Drivers can also find updates on reopening plans, detours and traffic conditions through the Commercial Street Bridge webpage and Pennsylvania's 511PA traveler information system.

The Commercial Street Bridge project is one piece of Pennsylvania's broader investment in transportation infrastructure. Under Gov. Josh Shapiro's administration, PennDOT says more than 20,500 road miles have been improved statewide, while work has advanced on nearly 1,900 state and local bridges.

The state's newly enacted budget also includes $775 million over the next two fiscal years for shovel-ready projects to repair state-owned roads across Pennsylvania.

Sources: PennDOT