Virginia transportation officials are proceeding with plans to add a lane to sections of westbound Interstate 66 inside the Capital Beltway in line with Gov.-elect Timothy M. Kaine's desire to widen the highway, a project he identified as a priority shortly after his Nov. 8 victory.

By the end of the year, transportation officials hope to begin environmental and design work on interim improvements that would add a third lane to three trouble spots -- between Fairfax Drive and Sycamore Street; Washington Boulevard and the Dulles Access Road; and Lee Highway/Spout Run and Glebe Road.

The state has the $28 million needed to build the 1.5-mile lane between Fairfax and Sycamore but has not set a date for construction to begin. There is no money available as yet to cover the $34.6 million needed for the other two sections, state officials said.

The officials said the lanes could be added within the road's right of way. In certain spots, shoulders would be narrowed or eliminated so that no homes would have to be removed.

At the same time, officials are exploring a more ambitious plan to add a third westbound lane all the way from Scott Street in Rosslyn to the Dulles Access Road as a result of a study commissioned last year by Gov. Mark R. Warner (D). The cost would be $112 million to $233 million, depending on whether the lane was reserved for buses or carpools or carried a toll.

I-66, which runs 77 miles from Strasburg, Va., to the District, carries tens of thousands of commuters from Northern Virginia's fast-growing western suburbs to job centers in Dulles, Tysons Corner and Washington. State officials have widened several parts of I-66 outside the Beltway, including the addition of four lanes west of Manassas, but they have not been able to overcome local opposition to adding lanes inside the Beltway.

Supporters say lanes are needed there because the highway jams daily in both directions during peak morning and evening hours. It also clogs regularly on weekends and even at night.

Plans to widen the highway inside the Beltway became an issue during this year's campaign for governor when Republican candidate Jerry W. Kilgore promised to add lanes in both directions. During the campaign, Kaine (D) supported the Warner plan on the westbound side and has since said he would like to explore a similar approach on eastbound I-66.

Delacey Skinner, a Kaine spokeswoman, said Kaine plans to bring together transportation officials, elected leaders and residents to discuss adding an eastbound lane. She said a key factor would be whether the lane could be built within the road's right of way. Transportation officials have not studied that question.

The plans for westbound I-66 are the latest chapter in the road's tortured history.

In 1959, plans for the highway were added to the map of the national interstate system. In 1970, Arlington County residents filed a lawsuit to block its construction. The suit was thrown out. But opposition delayed construction inside the Beltway until 1977, when an agreement was reached to build four lanes.

The agreement, named after U.S. Secretary of Transportation William T. Coleman Jr., excluded truck traffic, restricted I-66 inside the Beltway to carpoolers during rush hours and carried a promise that it would be left at four lanes.

Those lanes were completed in 1982. Four years later, Metro's Orange Line to Vienna opened. In 1999, the Coleman agreement was undone, and the governor, James S. Gilmore III (R), announced plans to widen the highway in both directions. A widening study was dropped in 2003, but later that year, Warner agreed to a study on adding a single westbound lane.

The Arlington communities along I-66 have opposed adding lanes because of concerns about noise, pollution and spillover traffic congestion. They also believe the spirit, if not the substance, of the Coleman agreement should live on.

Some in the county also oppose widening the highway because they believe it will hasten the type of suburban sprawl that would require more highways. The Arlington County Board also opposes widening and passed its most recent resolution against it in the spring.