Virginia Highway Commissioner Harold C. King told Northern Virginia officials yesterday their complaints about a controversial ramp metering system being installed on Shirley Highway and I-66 had come too late and said the ramps probably will become operational this fall.

King turned aside requests from Fairfax County and Alexandria lawmakers to stop construction of the new computerized system designed to speed the flow of rush-hour traffic in and out of Washington. "What you are talking about is after the fact," the commissioner said. "That decision was made two or three years ago."

The local officials fear that the traffic-control lights being installed on the ramps will cause traffic backups, give preference to commuters from the outer suburbs and create congestion on neighborhood streets.

Fairfax and Alexandria have threatened to go to court to try to block the state from implementing the controls. They argued yesterday at a 45-minute meeting in Fairfax City that the millions of dollars appropriated for the system could be put to better use improving area roads.

King said the localities should have known about the project when it was initially approved last year.

"I wasn't aware of it," said Fairfax Board Chairman John F. Herrity.

"Fairfax County was aware of it," replied King, prompting Alexandria Mayor Charles E. Beatley Jr. to say: "The highway department has always been after the fact."

King's department said the $22.9 million computerized traffic control system will reduce accidents on the highways 20 to 40 percent and increase average rush-hour speeds from below 30 miles an hour to an average of 40 miles an hour.

King and two consultants spent much of the meeting giving officials a history of Shirley Highway and of the success of ramp metering in California and Chicago.

Because of another meeting, King said he was not able to stay and answer most of the officials' questions. He did offer to meet with them again to answer the remaining queries.

That wasn't enough to make all the officials happy. "I'm upset that the highway department came here, and made a presentation of a dog-and-pony show, and then left at the point that we were going to ask questions," Alexandria City Councilman Carlyle C. Ring said after the meeting.

During the meeting, Ring requested that fourth lanes, which have been added to Shirley Highway between King Street and Glebe Road northbound; and between Shirlington and Duke Street southbound as part of the traffic control program be opened to traffic before the ramp metering is implemented.

State highway officials argued against opening the extra lanes, saying that without the ramp metering the lanes would merely attract more cars and traffic again would bog down.