Almost a decade after Metro's lines into Fairfax County were planned, county officials say millions of dollars of road improvements must still be made to provide adequate access to some of the future Metro stations.

Members of the county board of supervisors toured the future Vienna Metro line yesterday, then talked about asking voters to approve a bond issue to make road improvements around two of that line's stations -- at West Falls Church and Dunn-Loring -- and at the Huntington and Franconia-Springfield terminals outside the Capital Beltway east of Shirley Highway. The stations are scheduled to open over the next five years.

Without the improvements, some supervisors said, there could be massive traffic jams that could cost commuters more time than the actual rail trip into the District of Columbia.

"We'll have to go to a bond issue -- there's no question about it," said Supervisor Joseph Alexander (D-Lee) as he toured the Vienna line with the other supervisors. He said there is no concensus yet on the amount the county will seek, but estimated it to be "in the millions."

"The burning issue in this county is transportation. People want the Metro system and they want access to it," he said. "I don't think we will have any trouble getting them to approve it."

The county would first have to persuade the Virginia legislature to give its approval for spending county funds on highways. Only the state may now construct roads within the county. County board chairman John F. Herrity, a Republican, said he expects a bond referendum to be held in November 1981 if the legislature approves.

Recent reductions in gasoline consumption by motorists have cut sharply into state gas tax revenues, which resulted in the state's cutting $37 million from its road-building program.

Virginia highway officials recently slashed an allocation that would have aided the Huntington station, reducing to only $100,000 the amount granted to widen a major station access route from two lanes to four. That station is set to open in 1982.

The supervisors also voiced concern about the West Falls Church Station, where current plans limit local access to one two-lane road, and the Dunn-Loring station, to be located in the median of Rte. I-66 but which will have no vehicular access to that highway.

Current plans call for most commuters to ride buses to the Fairfax Metro stations. Supervisor James Scott (D-Providence) predicted that motorists who try to drive to the stations could face traffic snarls of up to 45 minutes unless access is improved.