With a practiced eye, engineer Steve Bartkovich scanned the underbelly of the Dannehower Bridge carrying U.S. 202 over the Schuylkill, evaluating Rorschach-like rust splotches on steel girders and checking concrete for signs of crumbling.

Bartkovich, a PennDot civil engineer for 13 years, was there to inspect the steel substructure of the bridge, checking particularly on how some previous repairs were holding up.

Every so often he’d peer over his shoulder or scan the near horizon toward the Norristown side for a different hazard: peregrine falcons, a threatened species that nest on the bridge.

» If you value this kind of journalism, please subscribe today.

“They’ll swoop down and knock off your hard hat,” said Bartkovich, 37, a PennDot bridge inspector.

Most people don’t think about steel fatigue or the corrosive power of road salt and water during the few moments it takes to drive across a bridge.

Bartkovich and an army of inspectors do it for you, on watch to prevent bridge failures.

On Jan. 28, the stakes became frightfully clear as a steel-frame bridge carrying Forbes Avenue 150 feet above a creek in Pittsburgh’s Frick Park snapped. It fell with a thunderclap and a roar that lasted a full minute, as captured by doorbell cameras in the nearby Regent Square neighborhood.

Several cars plunged into a gorge, and an articulated transit bus dangled on the broken bridge deck. Nobody died, but 10 people were injured. The National Transportation Safety Board is investigating the colossal failure.

And yet the Fern Hollow Bridge was not considered especially dangerous. Its condition was rated “poor” — the same as 512 roadway bridges in the Philadelphia region with average traffic of 100 or more vehicles a day, according to an Inquirer analysis of federal data.

That equates to about 13% of the 3,901 bridges in Philadelphia and its surrounding seven counties that carry cars or trucks, according to the Federal Highway Administration’s National Bridge Inventory for 2021, based on inspections performed every 24 months by state transportation departments.

A “poor” tag doesn’t mean that a bridge is about to collapse but that at least one of its three primary components — the superstructure, the deck, and the substructure (or culvert) — has shown signs of deterioration serious enough to warrant closer scrutiny or repair.

“Similar to evaluating a person’s overall health, a bridge condition is just far too complex to really be fully described with three condition ratings,” said Melissa Batula, the acting executive deputy secretary of PennDot.

It’s not clear how many times bridges have collapsed in the United States, but it’s pretty rare, especially given how much wear they take from the weather and modern traffic.

The NTSB has investigated at least 16 serious highway bridge collapses since 1967.

When it does happen, it’s horrifying.

In 2007, for example, much of the eight-lane I-35W bridge in Minneapolis fell into the Mississippi River during evening rush hour, killing 13 people and injuring 145. In 1987, the New York Thruway (I-90) bridge over the rain-swollen Schohaire Creek collapsed in Amsterdam, N.Y. Ten people died.

About 178 million daily trips are taken across the nation’s 46,154 structurally deficient bridges rated in poor condition, according to the 2021 infrastructure report card by the American Society of Civil Engineers.

Pennsylvania, an old state, has the second most poor-rated bridges in the United States based on 2020 data. PennDot says it has reduced the inventory of state-owned poor bridges by more than half since 2008, from 6,034 to 2,433 now. The state had prioritized tackling bridge maintenance, and a 2013 increase in the wholesale fuels tax pushed by former Gov. Tom Corbett helped fund repairs.

The Republican chair of the state House Transportation Committee, Rep. Tim Hennessey of Chester County, and State Rep. Mike Carroll, the committee’s ranking Democrat from Luzerne County, say they are preparing legislation this month for a $500 million local bridge trust fund to help strapped municipal governments fix deteriorating spans.

And the $1.5 trillion federal Infrastructure Act, passed in November, built in an incentive for states to spend money fixing sometimes-overlooked locally owned spans. Transportation Secretary Pete Buttigieg announced new funding for bridge repairs on Jan. 14 in Philadelphia, standing before the rusting bridge that carries Martin Luther King Jr. Drive over the Schuylkill. It’s closed to vehicles because of deterioration, but cyclists, runners, and walkers flock to the crossing.

Under the new policy, federal money will cover 100% of the cost for work on spans owned by counties, towns, and cities — but 80% of costs for bridge projects on interstates and designated federal highways.

“Our hope is that ... can really unstick a lot of projects,” Buttigieg said.

Though bridge conditions are public records, they are not designed as an early warning system for drivers.

Rather, Batula of PennDot said, the system is meant to “generally categorize” the safety of bridges and “provide a global view” to help officials identify priorities and schedule patches, improvements, and replacement projects.

There are gradations of “poor,” though, based on the severity of wear or damage to the critical structures of a bridge.

To make the call, inspectors like Bartkovich rate each component on a scale of 0 to 9 against a detailed set of engineering standards. Four or below equals poor; the lower the number, the sooner repairs are needed. Engineers use the worst single rating to decide a bridge’s overall score.

Of the bridges in poor condition in the Philadelphia region, 40 are closed, with most awaiting repairs, and 206 have some type of safety restriction, such as vehicle weight limits, according to the federal database.

Almost 265 area bridges had a lower numerical score than the now-crumpled Fern Hollow Bridge on Pittsburgh’s east side. It was used by about 14,500 vehicles a day, and was considered safe.

Now the federal government is showering states with $26.5 billion for bridge repairs over the next five years. Pennsylvania is to get $1.6 billion, New Jersey, $1.1 billion.

And academics are researching ways to improve bridge safety, including efforts to design remote, wireless monitoring systems with artificial intelligence programs to crunch the data points.

PennDot also takes steps to protect weaker bridges, said Mike Keiser, acting deputy secretary for highway administration. Besides weight limits, it runs a permit program that tracks truckers with heavy or oversize loads and routes them away from potential trouble, he said.

After Tropical Storm Ida caused serious flooding last year, agency inspectors fanned out for emergency checks of hundreds of “scour critical” bridges prone to erosion beneath their foundations. Rushing floodwaters and debris can make the problem worse.

“The public should be very much assured that we’re doing everything we can to make sure our infrastructure is safe,” Keiser said.

In the system of triage bridge engineers use, the Dannehower Bridge is not yet a problem. It is rated in fair condition but is monitored closely because it had minor cracks in some steel deck supports during a scheduled inspection, which were repaired.

The fixes seem to be holding up well.

“This one is in pretty good shape,” Bartkovich said on a recent visit, yards from the Upper Merion Vikings’ crew-team boathouse. “Hopefully we don’t have to do any major rehabs anytime soon.”

A lot of information is visible to a trained bridge engineer, he said: Inspectors look for “spalling,” or crumbling of concrete that can indicate or lead to structural failure; cracks in steel; places where steel is bent out of alignment; settlement around foundation structures.

If there’s uncertainty, inspectors can conduct “nondestructive” tests by banging a hammer or dragging chain on deck concrete to find hollow-sounding pockets and using penetrating dye and magnetic particle tests to outline steel cracks. In some cases, they deploy a robotic device called a RABIT that scans a bridge’s deck with ground-penetrating radar to generate a high-resolution map of flaws.

None of that would be needed at the Dannehower Bridge this day. Built in 1968, the bridge spans the Schuylkill, Bledsoe’s Island, and rail tracks and a surface street in Norristown.

And good news for inspectors: No falcons were flying patrols.

Bridges in need of upkeep traverse all kinds of terrain in the region, as well as roadways of rail and concrete and links between suburban towns. They add a pastoral touch to parks. They are made of steel, concrete, or masonry and carry up to tens of thousands of vehicles a day.

At least eight poorly rated bridges on I-95 soar over city arteries, though some have since been refurbished as part of ongoing construction and their rating may have changed. Spans over Tacony, Fraley, and Comly Streets average more than 200,000 vehicles a day.

Since the freeway is elevated, thousands of rushing motorists probably don’t notice. Or many other bridges, for that matter.

One mile west of the interstate, for example, more than 40,000 cars and trucks a day rumble over a steel-girder bridge on Route 322 in Upper Chichester Township, Delaware County. Built in 1949, it passes over CSX Railroad tracks and got scores of 3 (with 9 being best) for the condition of both its deck and substructure.

One of the 94 Philadelphia bridges in poor condition, the 20-foot stone masonry arch over Wissahickon Creek on Valley Green Road, was rebuilt in 1915 and averages about 100 vehicles a day, a possible undercount because it’s based on data collected in 1982.

The bridge is rated poor because of scour, or erosion below the waterline, on the east abutment, city officials say. It’s still safe but has a 5-ton vehicle weight limit to help extend its life.

A similar bridge nearby that carries Bells Mill Road over the creek has similar problems. After scour damage was noted several years ago, divers made repairs, which have held.

“These [old] bridges were not designed to handle the size and weight of vehicles on the road today, and even when in good shape are ‘functionally obsolete,’” said Keisha McCarty-Skelton, spokesperson for the city Streets Department. The bridge has a 3-ton limit.

» READ MORE: A timeline of the country's oldest active stone bridge

Other findings from The Inquirer’s analysis of the federal data on spans in the region:

One caveat: Data are based on information each state submitted to the Federal Highway Administration last year, so the status of some bridges may have changed.

Ivan Bartoli, an associate engineering professor at Drexel University, and Marcello Balduccini, a computer scientist at St. Joseph’s University, are trying to push the boundaries of how to detect bridge problems.

With a federal research grant, they are developing a system capable of wirelessly monitoring bridges — much as a fitness tracker on a person’s wrist can measure health indicators — and to use artificial intelligence to analyze reams of readings.

Placing sensors in critical spots assesses how displacement, vibration, acceleration, fatigue, and stress affect the materials in structural components, said Bartoli, who specializes in safety monitoring of major infrastructure.

“A bridge is always moving, even if the motion is tiny,” he said.

Wired sensors are used on a small percentage of bridges, but they are not as flexible and cost more. The idea is to give human bridge engineers a dynamic new tool that would make risk assessments more precise “and allow you to prioritize where to invest infrastructure money,” Bartoli said.

Once information is transmitted, it would be uploaded to the cloud, and then the machine-learning system the St. Joseph’s team is designing would organize the data points, synchronizing them with one another as well as with time-stamped video, Balduccini said.

“The machine will need to interpret what is normal and what is not and tune out the noise,” said Balduccini, director of the Haub Innovation Center in the university’s business school. Basically, coding that is more like a script than a series of commands will enable the system to think, he said.

With AI programming, a computer system is “able to deal with [some] uncertainty and ambiguity,” such as narrowing a diagnosis to two options or asking for more information, Balduccini said. The machines will flag issues for engineers on the ground.

Wireless bridge monitoring could help the country begin to catch up after decades of underinvestment, Bartoli said.

“Infrastructure in general has the curse that it gets recognized only when something is wrong,” he said. “People don’t really think about it, unless, say, they can’t get their Amazon package.”

“Failures are rare, and that’s due to the professionalism of the engineers at PennDot and across the country,” he said.

The goal is to get even better.