The Fairfax County Board of Supervisors was planning strategy yesterday to persuade voters to approve a $134.4 million bond issue for road improvements -- the largest bond issue ever to go to referendum in the county and believed to be the largest ever proposed for roads in the state.

If the bond issue is approved by the voters in the fall, the county would borrow money to build two segments of the long-awaited, cross-county Springfield Bypass, which would swing across Fairfax from Leesburg Pike (Rte. 7) in the northwest to Richmond Highway (Rte. 1) in the southeast.

The bond issue also would pay for 12 other major road construction projects designed to ease traffic for commuting and cross-county travel.

The supervisors' decision early yesterday to ask the Circuit Court to schedule the referendum was hailed as a milestone in an effort by Fairfax, Virginia's wealthiest jurisdiction, to take over most of the local road-building responsibilities assumed by the state since the Depression.

County board Chairman John F. Herrity, a leading advocate of the Springfield Bypass for a decade, said he had already scheduled about 20 speaking engagements to urge voter approval of the bond issue.

"I certainly intend to be out on the hustings on a regular basis . . . just like a political campaign," said Herrity, a Republican. He said Supervisor Joseph Alexander, a Democrat whose Lee District in southeastern Fairfax contains about a third of the non-bypass road projects, "is going to be really cranked up" in pushing for the bond to pass.

Supervisor Elaine McConnell (R-Springfield), many of whose constituents would use the Bypass to travel cross-county, said she, too, plans to speak out frequently this fall for the bond package.

The supervisors' pitch is likely to stress the balance of transportation interests served by the bond package, officials said.

Herrity said his emphasis will be that the road projects appearing on the ballot will help commuters get to Metrorail stations and onto I-95 and I-66, and also benefit the growing number of Fairfax residents who work within the county.

At the meeting that preceded the vote on the referendum, Herrity urged fellow supervisors not to add road projects in their districts to the bond proposal, saying he feared that could lead to charges of pork barrel politics.

As it turned out, there were no additions to the package, but there was one substitution. At the request of Supervisor Audrey Moore (D-Annandale), the board deleted a widening of Rolling Road in her district, replacing it with a widening of Guinea Road, which Moore said is a more pressing need.

The bond issue proposal includes about $90 million for the two segments of the Springfield Bypass. Of the other projects, the largest also is expected to be the most controversial -- a $13.2 million extension of S. Van Dorn Street to Lockheed Boulevard, which runs into Rte. 1.

The extension would slice through Huntley Meadows Park, a 1,262-acre county park that is one of the few remaining natural wetlands in the region. Environmentalists say the road would harm the ecology of Huntley Meadows, which is home to dozens of species of birds, animals and insects.