The Fairfax Board of Supervisors endorsed a watered-down version yesterday of proposed state legislation meant to help a Northern Virginia developer force developers of nearby projects to pay him back for road improvements.

"It's a Batman relief fund," said Chairman Audrey Moore, referring to J. Bahman Batmanghelidj, who is seeking the legislation. Moore warned fellow board members they were taking a risk by backing the proposal, saying the bill "could create all kinds of havoc in the county."

Moore, a Democrat who is seeking reelection this year, is expected to run a campaign that portrays developers and builders as a negative influence on the county.

Batmanghelidj, builder of a retail, residential and office project near Dulles International Airport known as McNair Farms, is seeking legislation to require nearby developers to reimburse him for some of the $28 million in road improvements he provided in an agreement he made to gain rezoning. He declined to reply to Moore's comments.

The legislation, while introduced specifically to clarify Batmanghelidj's situation, could be applied to other projects in the future.

Batmanghelidj said it is necessary because he has an agreement with Fairfax County to help him get reimbursed but state law does not now give the county authority to get involved. He has said he donated more road improvements than was necessary to serve his project because he thought he would get some of his money back.

After a half-hour discussion, the supervisors voted 5 to 3 to support the bill if it were rewritten to leave the decision to implement the policy up to the county and not the state. If the county approved the policy at a future date, it would apply only to developers who sought rezonings after the board made its decision.

Supervisors Kate Hanley (D-Providence) and Lilla Richards (D-Dranesville) joined Moore in opposing the proposal. Supervisor Joseph Alexander (D-Lee) was absent.

"My purpose isn't to help any individual," said Supervisor Martha V. Pennino (D-Centreville), who spearheaded the board's support. "Rather, it's to establish a policy where we can get roads built when we don't have public funds to build them. There's no question it became controversial because of Batman."

But some county staff members took a dim view of whether the legislation would help them find new sources of road funds.

"In the long run, the board may be getting less money than they would have before," said Anthony H. Griffin, deputy county executive for planning and development.

In other action yesterday, the board voted 7 to 1 to support proposed state legislation calling for a limit on property assessments. Richards opposed it.