JOHNSTON COUNTY -- In recent weeks, drivers likely noticed the orange-vested work crew toiling on a narrow, two-lane bridge over the Neuse River on N.C. 42.

The crew spent three weeks cleaning rusted rebar and patching crumbling concrete within the bridge’s support structure.

Jimmy Marler, an engineer with the N.C. Department of Transportation, said moisture from the Neuse had seeped into the cracks of the bridge’s pylons, causing the rust and crumbling concrete. He said the problems had been fixed and that the bridge was safe.

But that doesn’t necessarily mean an end to the troubles for one of Johnston County’s oldest bridges. Federal and state inspectors charged with determining a bridge’s sufficiency rating — the overall measure of a bridge’s condition — most recently gave the N.C. 42 bridge a score of 4 out of 100.

Sufficiency ratings are calculated using a formula defined by the Federal Highway Administration. The formula places 55 percent of its value on a bridge’s structure, 30 percent on its serviceability and 15 percent on whether the bridge is essential to the public.

In Johnston, other bridges with similarly low scores are on Cornwallis Road over Swift Creek, a score of 5; northbound Interstate 95 over the Little River, 6; and N.C. 50 over Black Creek, 7.

The ratings have met with renewed interest in recent weeks. One year ago, the collapse of an eight-lane bridge on Interstate 35 in Minnesota killed 13 people. The tragedy also brought immediate calls for repairs to bridges across the nation.

In addition to assigning a sufficiency rating, the FHA also assigns other labels to troubled bridges. Of the nation’s 590,000 bridges, about 12 percent are classified as functionally obsolete. That means a bridge is either too narrow, too short or is prone to flooding. In Johnston, 33 of the county’s 213 bridges are functionally obsolete.

About 80,000 bridges nationwide are classified as structurally deficient. That means load-bearing elements of the bridge have deteriorated significantly or that the waterway opening provided by the bridge is insufficient. Thirty bridges in Johnston County fall into that category.

Marler didn’t specify which bridges in Johnston had earned those titles. But he suggested, for example, that the bridge on N.C. 42, which earned the lowest sufficiency rating of any bridge in the county, might be considered obsolete. Still, he cautioned drivers from panicking over numbers and labels.

“A [score of] 4 doesn’t mean the bridge is unsafe for travel,” he said of the bridge on N.C. 42. “It probably just means that the structure is extremely old. These ratings are inevitably going to fall over time because bridges are exposed to the elements. They all show wear over time.”

A recent Associated Press review of North Carolina’s efforts to address its bridge needs since the Minnesota bridge collapse showed slow results. According to the AP review, North Carolina has repaired 10 percent of the state’s most-traveled structurally deficient bridges in the past year.

The state DOT told the AP that it had been focusing more on maintenance and had received federal money to speed up bridge replacement. Marler said the list of Johnston bridge projects had only grown since last year’s tragedy.

“We have a constantly evolving work plan,” he said.

In Johnston, Marler said, upcoming projects include repairing bridges on N.C. 210 over Swift Creek in the McGee’s Crossroads community and on Covered Bridge Road over Buffalo Creek in the Archer Lodge community. Work on the N.C. 210 bridge might begin as early as this week. Repairs to the bridge on Covered Bridge Road could start within a month, Marler said.

Also, the DOT’s Transportation Improvement Plan for 2007-2015 shows that the federal government will pour millions of dollars into replacing nearly two-dozen bridges in Johnston in coming years. Among the projects already receiving funding are the bridges on U.S. 70 Business over the Neuse River and on N.C. 50 over Black Creek.