The Fairfax County Board of Supervisors on Tuesday approved a $1.4 billion transportation package that, over the next six years, will pay for wider roads, highway interchanges and new sidewalks across the county.

Funded primarily through new state tax dollars provided under a transportation law approved by the legislature last year, the county’s spending program will target some of Northern Virginia’s most congested highways, including portions of Interstate 66 and the Dulles Toll Road.

County transportation officials also intend to install dozens of new sidewalks in portions of the rapidly growing county that still have rural roads.

“This is a major, major action,” board Chairman Sharon Bulova (D) said before the unanimous vote to approve the largest infusion of transportation money in Virginia since the 1980s.

Even so, the nearly 230 projects placed on a priority list by the Fairfax Transportation Department represent only about half of the transportation needs in one of the country’s most traffic-choked counties.

And many projects are likely to take years to be completed, county officials warned.

“We need to be careful that message is clear to people,” said Supervisor Pat Herrity (R-Springfield).

“It doesn’t mean it’s done in three to six months, much less six years.”

The list of recommended projects is a product of months of public hearings held by the county Transportation Department at which residents often vented frustrations over not being able to get to work on time or walk through their neighborhoods without fear of being hit by a car.

“People are almost emotional,” said Supervisor John W. Foust (D-Dranesville).

“They’re trapped in their homes, and they want sidewalks,” he said.

About $1.2 billion in funding is expected from the state transportation law, said Tom Biesiadny, director of the county Transportation Department. The rest comes from county tax revenue and other sources.

Supervisor Linda Q. Smyth (D-Providence) cautioned county officials to spend the money judiciously, saying that the county should coordinate with developers and lean on them to pay for road or sidewalk improvements whenever possible.

In situations where plans are underway to improve a particular piece of land, she said, “let’s not spend our money only to have a developer come in and tear up the sidewalk.”