The 1986 session of the Virginia General Assembly opens Wednesday for what could be one of its most divisive sessions, widening the already bitter rift between urban and rural legislators over the critical issues of how much to tax and spend for roads and schools.

The key player in the battles is expected to be a man who hasn't taken office yet: Democratic Gov.-elect Gerald L. Baliles. He begins his term Saturday, succeeding Charles S. Robb, whose administration began twin efforts to pump more money into both highway construction and public education.

Baliles, 45, a former state attorney general and legislator, won the state's top office, promising to expand the Robb programs. The governor-elect already has fueled the controversies with his appointments of new administrators to oversee the highway system, one of the most powerful and controversial state agencies.

A number of other issues -- among them legislation that would mandate seat belt usage, impose more precise ethical standards for legislators and regulate second-mortgage interest rates -- will be up for consideration.

The question of legislator ethics grew more intense today when the Acting Attorney General William Broaddus announced he would initiate prosecution of conflict-of-interest charges against state Sen. Peter K. Babalas of Norfolk, the fourth-ranking member of the Senate. Details on Page D1.

The issue that brought Babalas into a swirl of controversy -- his vote to kill regulations for the state's second-mortgage lenders -- is certain to be pressed, as will demands that the state do more to regulate what Babalas contends are the inevitable conflicts the lawyer-legislators must face when dealing with issues that affect their legal clients.

This will be a 60-day session -- a long one by Virginia standards -- and few issues are likely to occupy as much attention from the 140 legislators as how to divvy up the state's $18 billion-plus budget for the two-year period that begins July 1.

Probably no budget questions will attract as much debate as whether to impose a tax increase to boost funding for the state's roads, which legislators from all sections of the state agreed need improving, and how to apportion state aid to local schools.

New taxes may be needed, and that makes many legislators nervous. "Last year we just rearranged the money," said Del. Ford C. Quillen (D-Scott). "This year it's raising money. It's a much more difficult issue. People's nerves will get raw."

Northern Virginia has large stakes in both issues. Millions of dollars in state funding for the region's schools and funding for roads as well as the Metro system are certain to be challenged by officials who say the Washington suburbs are too wealthy to receive extensive state aid.

"This year, for us, it's not losing money," said Fairfax County Supervisor Audrey Moore, a Democrat sounding the fear of many Northern Virginia officials. "The biggest single problem is Metro money. We've got to hang in there and keep it from being taken away from us." Last year the Metro opponents tried and failed to eliminate the region's $21 million Metro appropriation.

While some elements of the debate may be old, this year's debates will be played out with a new cast of characters. The fall elections brought Baliles to power with the state's first black lieutenant governor, L. Douglas Wilder of Richmond, a former state senator, and the first female state attorney general, Mary Sue Terry of Patrick County, a former state delegate.

Northern Virginia will gain additional clout with the elevation of three Democrats to key chairmanships, Del. Dorothy S. McDiarmid of Fairfax to the House Appropriations Committee, Del. Mary A. Marshall of Arlington to the Cities and Counties Committee and Sen. Joseph V. Gartlan of Fairfax to the Senate Elections Committee.

Baliles has given additional encouragement to the Washington suburbs, which supported his election, with two key appointments, Fairfax Del. Vivian Watts to his cabinet as secretary of transportation and public safety, and Ray D. Pethtel, who had been director of a legislative oversight commission to replace State Highway Commissioner Harold C. King.

What role the Republicans, who gained only one member in the House of Delegates in the fall elections and remain a distinct minority, will play is uncertain. Demoralized after their party's second consecutive loss in the statewide elections, the House GOP Caucus recently ousted the mild-mannered Del. Vincent F. Callahan of McLean as minority leader. The Republicans replaced him with Del. Raymond R. (Andy) Guest of Warren County, who told the caucus today that he will be "as fair as I know how and as rough as I've got to be" with the Democrats.

Full funding of the state's share of the so-called Standards of Quality in Education has been pledged both by Robb, who has primary responsibility for preparing the fiscal 1987-88 budget, and Baliles. To meet that goal will require a lot of state money, and Northern Virginia officials are fearful that since theirs is the richest section of the state they will will get proportionately less of the added state aid.

"We're liable to get cut in education," said Fairfax County Supervisor Thomas M. Davis III, a Republican. "When you take money out of categorical aid . . . Fairfax gets the short end of the stick. We'll lose bottom-line dollars."

The stage was set for a major debate when the state Department of Education announced last month that the state's full share would cost $419 million a year, while the Joint Legislative and Audit Review Commission projected the cost at $192 million. Where Robb comes down between those extremes will be known in his budget message Thursday.

Moreover, the legislators expect to wrestle with the effects of what Andrews calls "the biggest enigma" of 1986, the congressionally mandated federal deficit reduction that is expected to curtail federal aid sharply.

There is no talk here about a general tax increase, but there are plenty of balloons being wafted about how to finance road construction, and all of them call for new money, whether in the form of increased gasoline taxes, more toll roads or selling bonds. Last year the assembly restructured the state's highway construction formulas, taking money from rural areas and giving more to the rapidly developing urban areas.

That infuriated rural legislators, and they have promised to renew the battle as others are preparing to boost the state's gasoline tax.

Sen. Edward E. Willey (D-Richmond), the chairman of the Senate Finance Committee, said he will propose legislation to increase the gasoline tax by a penny from 11 cents a gallon and the cost of titling a car from 2 percent to 3 percent, which together he figures would raise $102 million a year.

A study prepared for the Virginia Association of Counties, however, estimated that a 3- to 3 1/2-cent increase in the gasoline tax, which was raised to its present rate in 1980, would generate only $100 million.

The study suggested that Virginia may have to abandon its traditional pay-as-you-go philosophy of financing highway construction. It said that if $100 million were instead set aside to pay off road construction bonds, during 20 years at 8 percent interest, it would allow construction valued at $770 million.

Senate Majority Leader Hunter B. Andrews of Hampton said the state's badly needed road construction "cannot be met within existing formulas" because maintenance and administrative costs, which take more than half the revenue, "come off the top."

Andrews said it is "always easy for you the media to say" that the issue will come down to an urban-rural battle, with farm area legislators arguing for a distribution formula weighted to miles of roads, compared with a miles-of-usage scheme favored by city and suburban representatives. "We need a blend," Andrews said. "There are certain rural needs, and there are certain urban needs."

He noted that Northern Virginia representatives are pressing for money for the Springfield Bypass, an "outer beltway" and numerous other roads. His own Hampton Roads area, which has lost several key legislative positions, is seeking at least $50 million to complete a circumferential highway, and rural Southside wants $30 million to widen a stretch of Rte. 58, known as Suicide Alley, that has claimed two dozen lives in the last two years.

Legislators said they plan to confront a myriad of other issues, ranging from attempts to tighten drunk driving laws to such perennials as a state lottery and deposit on bottles.

While the session is likely to be issue-oriented, if postelection activity is a harbinger, partisan politics will be alive and well during the 1986 session. Baliles brings to the job of governor "the best background of anyone in history," according to Del. Alson H. Smith (D-Winchester).

But the new governor is likely to get less than the free ride Robb enjoyed from the minority Republicans, who were about as challenging to the Democrat as the Tampa Bay Buccaneers were to the Chicago Bears football team.

Two possible 1989 Republican standard-bearers, Rep. Stan Parris of Fairfax and former attorney general J. Marshall Coleman of McLean, have served notice that they are prepared to critique the new administration.

Del. A.R. (Pete) Geisen (R-Augusta), head of the GOP House caucus, issued an uncharacteristic blast Friday about the dismissal of a drunk driving charge against Sen. Richard J. Holland (D-Isle of Wight).

"The dismissal appears to be an example of political cronyism that results from single-party control of the political process," Geisen said. The Democratic prosecutor, who said he dropped the charge "for the good of the commonwealth," announced he is reconsidering his action.