Over the next six years, Fairfax County anticipates receiving an unprecedented infusion of about $1.2 billion in transportation money to help alleviate the daily headaches along Interstate 66 and other clogged roads.

But traffic has gotten so bad in one of the most congested counties in the nation that even that much money will cover only half of what needs fixing, officials say. And now a scramble is occurring among neighborhood groups and others in the county of 1.2 million residents to persuade local officials to give their traffic woes priority.

“There are so many projects to do and not enough money,” said Nicholas Firth, whose South County Federation has for years complained about increasing backups on roads in and around Lorton. “Our area is filled with disaster zones.”

The transportation funding law, which went into effect in July, will steer about $6 billion toward highways, bridges and other projects that seek to lighten road congestion. About $1.9 billion will target Northern Virginia, with the lion’s share of money going toward pending projects in Fairfax that would be handled by state and local transportation agencies.

The landmark transportation plan was a victory for Gov. Robert F. McDonnell (R) that came after a generation of attempts to find a solution to Virginia’s mounting traffic problems. But now that the legislative battle has ended, officials are faced with another problem: how to spend the money.

“Getting the money is hard, but the way we figure out how to spend it is almost harder,” said Fairfax County Supervisor Jeff C. McKay (D-Lee).

County officials have compiled a wish list of 214 unfunded projects, a combination of road expansions, new turning lanes, pedestrian bridges and other fixes that the county says would cost about $3 billion in 10 years to complete.

The county hopes to steer as much money as possible toward traffic problems in increasingly dense and busy areas, such as Tysons Corner and Reston, said Tom Biesiadny, director of the county transportation department.

Officials are also looking for repairs on roads where traffic jams have ripple effects across the region, such as I-66 heading in both directions and the often-sluggish Fairfax County Parkway, he said.

To allow county residents to weigh in on what for many is a rage-inducing issue, Fairfax transportation officials and supervisors held a series of public hearings this month and conducted an online survey that, officials said, received nearly 2,500 responses before it ended Friday night.

With that feedback, the transportation department expects to recommend a list of projects to the County Board of Supervisors. In January, the board will decide where the money would be best used. Although the effort is rooted in an effort to distribute the money equitably, it could end up pitting one neighborhood against another.

“If it wasn’t perceived as a fair process, we’d be reaching for the pitchforks because it’s so important,” said Supervisor John W. Foust (D-Dranesville), adding that he believes that the transportation department will try to spread the wealth.

Where the best solutions lie may depend on which part of the c ounty you are in, said McKay, whose district includes older neighborhoods whose roads are often crumbling.

“There is a little bit of a debate going on, especially in the urbanized parts of the county, where people believe what we need is not new interchanges but improved quality in our infrastructure,” McKay said. “People are going to see these major regional projects being done, and then they’re going to look out their front door and wonder why their roads are still falling apart.”

The transportation law mandates that most of the new money — derived primarily from increases in sales and car titling taxes — go toward congestion relief through new construction and highway maintenance.

The requirement may force county officials to pass on funding some projects, McKay said.

Several of the larger projects county officials hope to tackle are in suburban and rural areas that are rapidly growing.

In Centreville, officials hope to reconstruct the interchange connecting I-66 and Route 28, an effort that would cost about $166 million, officials said.

Near Fairfax Station, the county wants to widen a portion of the Fairfax County Parkway between Ox and Rugby roads for an estimated $116.7 million.

Some groups argue that the county should focus on smaller, less-costly projects, saying more of those can be accomplished for the price of building one new highway interchange.

Others say that traffic can be alleviated by making it easier for people to walk or use their bikes.

In McLean, residents would like more sidewalks, particularly in areas near schools where children often have to walk on the side of the road.

Frequently, parents choose to drive their children to school because of safety concerns, said Sally Horn, president of the McLean Citizens Association.

While rural roads once made sense in the county, “we have a lot of congestion now, and having kids walk along the roads isn’t a smart thing,” she said.

In Mount Vernon, residents are campaigning for county officials to expand a four-foot-wide bike trail along a stretch of Fort Hunt Road. The narrow trail forces cyclists to balance between cars on one side and a metal road barrier on the other, which residents see as a public-safety issue.

“It’s basically a death trap,” said Catherine Voorhees, head of the transportation committee for the Mount Vernon Council of Citizens’ Associations.

Voorhees said her group has lobbied for that project and several of other improvements for years, without success. After the new transportation law took effect, Voorhees said, she sent binder folders filled with suggested improvements to local and state officials.

“You get no promises, no feedback at all,” she complained. “You just hope that they heard you.”