Plans for Interstate 73 cleared a major hurdle this week when a group of localities, government agencies and an advocacy group agreed to its general path from Roanoke to North Carolina.

The controversial road project has been under discussion for 16 years already, and Thursday no one could predict how much longer it will take before construction money can be found and builders can begin work.

Still, the agreement signed Wednesday clears the way for a final environmental impact statement to be issued by the Virginia Department of Transportation.

The pact also ensures that Roanoke County's Clearbrook area will retain a connection to the Blue Ridge Parkway, most likely on Buck Mountain Road.

After the environmental impact statement is issued, the Federal Highway Administration would review the project, meaning perhaps another year will be needed before engineers can start designing the road.

Money remains the biggest question.

The federal transportation bill approved in 2005 provided $8.6 million for I-73 work in Henry and Roanoke counties, but that won't go far.

In 2001, VDOT estimated the road's cost at $1.3 billion, a figure that was under revision Thursday.

Chuck Lionberger, a spokesman for VDOT, refused to speculate on even a ballpark estimate of the price because "the costs for materials now are so volatile."

The first construction work is generally expected to occur in Henry County because of that area's economic distress from factory closings.

The agreement seems to solidify I-73's corridor between Roanoke and Martinsville.

Government officials in Franklin and Henry counties welcomed the news, saying that I-73 will relieve increasing traffic problems on U.S. 220.

"It's a road that I think is just very important to our transportation future," said Wayne Angell, chairman of the Franklin County Board of Supervisors. "With the growth in the region and growth in the shipment of goods from the south of us, I can't imagine what 220 would look like in 20 years without some drastic improvement."

H.G. Vaughn, chairman of the Henry County supervisors, agreed, saying the new interstate will be needed to deal with the increase in truck traffic.

But the corridor may yet pose problems, particularly in Clearbrook, said Annie Krochalis, the smart-growth transportation coordinator for the Sierra Club. A Tennessee developer is seeking rezoning to allow a Wal-Mart Supercenter in Clearbrook. Roanoke County's plans call for other commercial development as well on that stretch of road.

"If we do go through with I-73, how does it impact the parkway, and if we're expanding U.S. 220 to I-73, why are we putting another big box there?" Krochalis said. "It just seems like there's too many things going on in that one corridor to add up and make sense."

Arnold Covey, the county's director of community development, said he knows I-73 is also planned for that stretch, but that it could be decades before it's built.

"There's a lot of unknowns, a lot of money that would have to be appropriated," Covey said.

Virginia might not be able to meet its 20 percent funding share right away in the 80-20 split with the federal government. With the Virginia General Assembly gridlocked over how to fund new road construction, it could be a long time before that happens.

In the meantime, Covey said, Roanoke County is trying to carry on with its plans while still keeping an eye on the future.

"We as the county are trying to stay involved, and knowing this is years down the road," Covey said, "but also be at the table if it ever comes about, so we can negotiate at that point."

Parties signing the agreement were: Roanoke; Roanoke County; Franklin County; Henry County; the National Park Service on behalf of the Blue Ridge Parkway; VDOT; the Federal Highway Administration; two historic-preservation agencies; and Virginians for Appropriate Roads.

The latter group had argued that Oak Hill, an Old Order German Baptist community in Franklin County, should receive government protection as a historic area. The group's signature on Wednesday's agreement removes that argument as a potential obstacle to construction of I-73.

Four years ago the same group played a key role in getting the VDOT-preferred route changed in Roanoke by persuading the U.S. Department of Interior to declare the city's Southeast neighborhood eligible for the National Historic Register. As a result, the corridor was changed to a crossing over Crowell Gap in south Roanoke County.