Fairfax Supervisor Audrey Moore, the Democratic candidate for county board chairman, yesterday called for a special referendum next spring on whether to approve the sale of $100 million to $150 million in bonds to pay for road and rail improvements.

Moore, who has represented the Annandale District since 1972, is trying to unseat Chairman John F. Herrity, a Republican who is seeking his fourth term as Fairfax's highest elected official. The election is Nov. 3.

The proposal for a multimillion-dollar bond referendum was the centerpiece of a plan Moore unveiled in a news conference yesterday as the "major transportation initiative" of her campaign.

Later in the day, at a candidates' forum, Herrity said he saw "nothing new" in Moore's proposal except the special referendum, which he said would "cost taxpayers a couple hundred thousand dollars." Herrity supports a November 1988 bond referendum for transportation improvements.

"Everyone I know on the board is in favor of a bond referendum next fall," Herrity said. "Holding it a few months earlier has nothing to do with the speed of building the roads."

Moore disagreed: "The reason I've asked for a special election is that we've got to do more, faster."

County Executive J. Hamilton Lambert said he did not know how much a special spring referendum would cost, but "it'd be expensive." The last such referendum was held in 1978.

Lambert has said that county officials probably will propose a bond referendum of at least $300 million for next fall's ballot. Of that sum, about $100 million would be for transportation. The largest portion -- $144 million -- would be for schools, and the balance would go to county and regional parks.

In the candidates' forum, sponsored by the Merrifield Business and Professional Association, Moore reiterated her longstanding view that development should be "brought into balance" with the county's transportation capacity. Herrity stressed the county's prosperity, which he described as "the envy, in terms of quality of life, to people throughout this country."

The two also clashed for a second straight day about whether Moore had been a wholehearted supporter of the Dulles Toll Road, a major commuter route that connects the Capital Beltway with Dulles International Airport. Herrity produced a summary of a 1979 board meeting that indicated Moore had voted against it; Moore said the summary was inaccurate. A verbatim transcript of the meeting could not be obtained yesterday.

The two independents running for board chairman, James S. Morris Jr. and R. Terry Robarge, each called for new leadership in Fairfax, blaming Moore, Herrity and the other board incumbents for having made a muddle of the county's transportation system.

In her news conference, Moore called for several other transportation initiatives. They included requiring developers to pay for more improvements to roads, sewers and other public works; adopting an official county map so developers would not build in the way of proposed roads; restructuring the public works and road planning departments, and devising a new financial plan for road improvements.

Moore did not give specifics on what she thought the bonds should be used for, other than the Springfield Bypass. Herrity has championed the road project for nearly a decade.

She joined several other candidates for the board in calling for a county transportation commission -- a measure that Herrity has neither supported nor opposed. A county committee is studying the idea.

Following the example of Gov. Gerald L. Baliles, who launched his term by undertaking a major transportation funding initiative, Moore said she would convene a group of the county's "best and brightest" to study new revenue sources for transportation improvements. The group would have 30 days to report to the board, she said.

Said Herrity: "The question is who can provide the leadership rather than forming another commission or study group."

The tension between Herrity and Moore seemed to increase a notch or two yesterday. Hitting Moore on what he described as her opposition to major road projects, Herrity declared: "You can run from your voting record, but you can't hide from it."

Moore responded by reeling off a list of road improvements that Herrity had opposed over the years.

At the luncheon that preceded the candidates' speeches, just as Herrity sat down to his meal, Moore walked up with her plate and sat next to him.

"Hi, everybody!" she sang.

Herrity grimaced.