Northern Virginia's state highway commissioners pledged yesterday to look into Fairfax County's complaints about the controversial $22.9 million computerized traffic-control system being installed on Shirley Highway and I-66.

Highway Commissioners T. Eugene Smith and Joseph M. Guiffre didn't make any promises to delay operation of the system until officials can study its possible impact on traffic in neighborhoods near Shirley Highway, as the county requested. Officials in Fairfax and Alexandria have threatened to sue the state over the system, and say they fear lengthy traffic backups at the traffic lights being installed on the highway's on-ramps.

"I think that probably unless we can come up with a speedy way to meet their the county's requirements, we will probably go ahead with it," said Guiffre after the meeting.

Earlier this month, Virginia's chief highway commissioner, Harold C. King, turned down requests to halt construction of the system, which was designed to speed rush-hour traffic in and out of Washington. The system is scheduled to be activated this fall.

In a meeting in Fairfax City, the area's two highway commission representatives listened as Fairfax County Board Chairman John F. Herrity and Supervisor Thomas M. Davis complained that the ramp metering system had been put in place without the county's knowledge or approval. "There has been no public hearing before any citizens of Fairfax County. There has been no public input," said Herrity. "The Highway Department has, in my view, unilaterally imposed this on the citizens of Fairfax County."