PITTSFIELD — People traveling Holmes Road in southeast Pittsfield get a little more time these days to admire the neighborhood as they wait for newly erected traffic lights to change.

That's due to something they can't see: the slow ruin of a beam that helps support a bridge over Housatonic Railroad tracks.

Travelers and city officials were surprised by the state Department of Transportation's decision last month to close a lane on a bridge located between Miss Hall's School and the Herman Melville homestead.

With only one lane open, traffic will continue to bunch up on both sides for at least a year as the DOT hurries to shape a repair plan on the busy route.

Judith Riley, a DOT spokeswoman, said the agency is expediting design work for what she termed a "comprehensive repair" that could start next spring. But that timing is tentative because repairs have to be coordinated with utilities and with the railroad's use of the track below.

"This construction timeline may move," she said.

Down below the bridge, its problems are written plainly on the undersides of several of the yard-wide concrete beams that provide the structural strength of the span. The bridge, built in 1977, is made up of 10 long concrete beams butted against one another side by side, a common building method in New England since the 1950s, according to the Federal Highway Administration's online bridge manual.

Also common, the FHA notes, are leaks that can develop in joints between beams. When those leaks develop, deicing chemicals make their way through the structure, causing erosion in metal reinforcing rods and "spalling" — when bits of concrete break away.

According to inspections and reports obtained by The Eagle, it was one beam in particular, the seventh from the north side of the bridge, that prompted the DOT to act.

A March study by AI Engineers of Boston, following up on problems detected in the DOT's every-other-year bridge inspection schedule, recommended that the 68-foot bridge be closed entirely. But because that step would remove a major traffic artery from Pittsfield's road network, a middle step was taken to keep traffic off the deck above the bad beam.

Barriers were erected on the lane on the south side of the bridge, resulting in all traffic crossing above beams that do not show dramatic weakening.

In a March 29 memo, Alexander K. Bardow, the state's lead bridge engineer, said the "superstructure" of the Holmes Road span should be replaced as soon as money can be found. But overall, he noted, the bridge "is in fair to satisfactory condition."

When the bridge received its routine inspection May 22, 2018, problems with beams were flagged as "severe." Inspectors noted that issues should be dealt with as soon as possible, one step above the urgency of "prioritize" in the DOT's rating system, but below "immediate" action.

That changed this year, when the outside engineering company conducted more tests on the bridge's ability to carry weight. Charts in that firm's nearly 100-page report are marked in red where it lists the amount of weight certain beams are able to withstand.

In short, no weight at all: "0 ton rating."

Riley, of the DOT, said troubles flagged by a routine inspection led the department to order an evaluation of how much "load" the bridge could tolerate.

"This evaluation highlighted an acceleration in deterioration in a major beam," Riley said, referring to the beam marked in reports as B7. "In order to ensure safe operation, the load on this beam had to be removed by restricting a lane of traffic."

From below, concrete is missing from a middle section of that beam above the tracks, exposing metal rods. The bridge crosses the north-south tracks at an angle, at least 18 feet above the rail bed, creating a cavernous and echoing space below. The ground is littered with bits of metal, an occasional nip bottle and the carcass of an old Commodore computer, Model 1702.

Even an expanse of graffiti on a bridge abutment — the structure supporting the east side of the beams — is flaking away with age. New rails and beams that are part of planned railroad improvements sit to the sides, awaiting use.

Up on the underside of the bridge's "superstructure," cracks and gaps appear between beams as well — a common problem with aging bridges, according to the Federal Highway Administration manual. Material appears to have fallen out on both sides of the seventh beam.

On a recent day, water could be seen dripping from various places beneath the entire bridge, including the area below the remaining travel lane.

"The joints between all beams have evidence of leakage," the May 2018 inspector report says.

Leakage is a common word in bridge inspection reports. These words are, too: Corrosion. "Jacking force." Delamination. "Flexural capacity." Spalling. "Dead load." Tears. "Reflective cracking."

The Boston engineering firm notes that while the seventh beam shows the most significant failure, other beams cannot support the loads imposed by certain types of vehicles as required by law.

The repair work, when it comes, will be the bridge's first reconstruction. In the meantime, engineers have called on the DOT to step up the frequency of inspections.

Larry Parnass can be reached at lparnass@berkshireeagle.com, at @larryparnass on Twitter and 413-496-6214.