Kevin Beachy has been overseeing the bridge replacement program for Alleghany County, Md., since 1985, when the county—located in Maryland's panhandle three hours west of Baltimore—adopted a different approach to rehabilitation and replacement.

“We used to try to do everything in-house when we had a six-man full-time bridge crew. But we had more bridges deteriorate than we could replace,” he recalls.

In just two decades, however, the county has cut in half the number of bridges posted at load restrictions (it is at 28%, down from 60%) by contracting out large projects and keeping the smaller, more manageable projects in-house—all without a dedicated bridge crew. Considering that both light and heavy manufacturing equipment as well as coal mining trucks travel the county's 550 miles of roads, that's quite a feat.

Over in Garrett County, Md., Dwight Emory uses some of his full-time roads department employees to act as seasonal bridge crews to plow snow on 700 miles of roads during the winter, just as Beachy does.

“With a contractor, you need time to get him in place. The benefit of going in-house is that you control the timetable and construction. It provides flexibility,” Emory says.

That is just one of several factors Beachy and Emory consider when planning a bridge project. Here are seven more things to consider:

The severity of the bridge's condition: Federal law requires bridges with spans longer than 20 feet to be inspected every two years, but Allegany County also inspects all smaller bridges every five years.

“If the state imposes a load restriction of three tons (6,000 pounds) or less, the bridge is closed immediately, and we have to do temporary repairs until it can be replaced. On the other hand, if we see a slow deterioration every couple years, then we know that in three or four years we'll have to do something, and we can actually program it in our budget with our own crews,” explains Beachy, a speaker at the 2008 National Association of County Engineers conference in Portland, Ore. “If there are major environmental impacts, and we have to go through the permit process (which lasts six to eight months) but the structure is collapsing, we consider that an emergency repair and go to a contractor.”

Abutments are the first thing Emory considers because the county's equipment cannot reconstruct concrete abutments for bridges with a clearance higher than 20 feet. “Our crews handle one or two minor structures each year plus one major structure,” says Emory, whose projects are limited by the type of equipment available to him.

The time of year: Maryland allows construction work in streams only from May through October.

Alleghany County crews average three to five projects annually (considering that construction season lasts six months, and each project takes two to three weeks to complete). “We don't have the luxury of having a bridge crew that can work 12 months of the year, but we're probably saving a quarter of a million dollars a year,” Beachy estimates, considering the salaries and benefits for five full-time employees.

“If we don't need to be near the stream, and the abutments are not in the flood plain, it can happen year-round— but it can be too cold for concrete work, and we're also not set up with heaters, so our crews can't work in below-freezing weather,” he adds.