The chief of the Virginia Department of Highways and Transportation has rejected a request by Prince William County officials to have a state-financed regional commuter rail study include the feasibility of extending Metrorail from Springfield to Lorton.

But regional transportation planners say they may be able to find other avenues by which the county's transportation problems can be studied.

The regional commuter rail study, which is being prepared by the Metropolitan Council of Governments (COG) at the state highway department's request, will examine the costs of implementing and operating commuter rail service from Fredericksburg to Alexandria and from Manassas to Alexandria using existing railroad facilities.

The request for expansion of the study was made by Del. David G. Brickley (D-Prince William) and Kathleen K. Seefeldt, chairman of the Prince William Board of County Supervisors. Both say they are concerned over increasing highway commuter traffic in the county and lack of funds.

Brickley and Seefeldt had asked Highway Commissioner Harold C. King to expand the final $50,000 phase of the study to examine a wider range of options than those originally considered. The new options include the extension of Metrorail from Springfield to Lorton, a "light" rail system paralleling existing railway lines and an improved express bus service to complement them.

"We have to make sure these people have a way of getting to work," Brickley said. "It would be a lot cheaper to connect with Metrorail at Lorton or to use a light rail system than to serve commuters on existing railway lines."

But King turned down the request, saying in a recent letter to Brickley that "broadening the scope of the study at this time would not be compatible with the completed first two phases and could thereby jeopardize the completion of phase three."

King said, however, he would have Richard C. Lockwood, the department's representative on COG's Transportation Planning Board, "request that the program committee place the discussion of a wider range of options" on the planning board agenda. The 24-member board is comprised of state and local government officials.

Lockwood has since done so and the policy-oriented program committee has referred the matter to the board's technical committee. It will be discussed July 8.

"Our technical committee will discuss how best to handle this request," COG Transportation Planning Director Al A. Grant said. He said the committee will consider "options for long-haul commuter travel and what form of study can be used to look at them."

Brickley, the General Assembly representative on COG's board of directors, said he was disappointed but not surprised at King's decision.

"The highway department is not one to be in favor of Metro and commuter rail, although they're better than they used to be," he said. Adding that not enough is being done to prepare for increased commuter traffic in the area, Brickley said, "We ought to be looking at plans for the year 2000."

He also said the first statewide commuter study since 1953, ordered by the General Assembly and completed in December 1982, focused on the use of car pools and van pools to the exclusion of other options.

Among the reasons "our roads are parking lots is the impossibility of widening routes 66 and 395 into Washington, the delay to 1989 for Metrorail service to Springfield and to 1987 in beginning phase-in of express lanes between Springfield and Dumfries," he said.

Prince William County has one of the fastest growing populations in the nation, nearly tripling in size between 1960 and 1980. Of the estimated 158,000 residents, more than 64,000 commute to work by private car. Another 2,100 use public transportation.

The COG commuter rail study estimates that had such rail service been available in 1982, commuters traveling to work along the Southern Railway line from Manassas would have numbered 1,800 and along the Richmond, Fredericksburg & Potomac Railroad line from Fredericksburg, 2,100 more. By 1990 those figures would have been 2,600 and 2,700, respectively, the study projected.

A sample one-way fare between Manassas and downtown Washington would be $1.50 by rail from Manassas to Alexandria and $1.10 by Metrorail from Alexandria to the District, making the daily cost of a round-trip commute more than $5 in today's dollars.

Usage estimates in the study reflect a fare structure that "results in 35-40 percent of operating costs being met by fare revenues," an indication that the commuter rail service would have to be subsidized.

But "VDH&T is prevented by state law from subsidizing rail operating costs," said William C. Jeffrey, an assistant transportation engineer with the department. "Therefore, those funds must be picked up by the localities."