Virginia's two likely gubernatorial candidates are beginning to craft plans to improve the state's transportation network, an issue that politicians expect will figure prominently in the contest next year.

While Lt. Gov. Timothy M. Kaine (D) and Attorney General Jerry W. Kilgore (R) have not outlined comprehensive plans on how they would pay for road and rail projects, they have begun to lay out some basic ideas.

Both men said in interviews Friday that they support a proposal for a state constitutional amendment that would prevent the government from tapping its transportation trust fund for other purposes. The revenue from the fund, which now contains $815 million, has been used three times since 1989 for purposes other than transportation, a fact that Kilgore and Kaine said diminished public confidence that money earmarked for public transportation is being used properly.

"We really have a credibility problem" when it comes to transportation projects, Kaine said. "Before anything, we need to make sure that money designated for transportation goes to transportation."

And Kilgore said, "Protecting the trust fund has to be a priority."

Both candidates also have said that they oppose raising the state's gas tax of 17.5 cents per gallon to fund rail and road projects, a plan that was floated during the 2004 General Assembly session and then removed from consideration.

Kilgore said he is looking to establish private-public partnerships and expand high-occupancy toll lane projects, which would allow motorists to either carpool or pay a fee for the privilege of driving in less-congested lanes.

In addition, he said, he is hoping to increase incentives for Northern Virginians to ride Metro and looking at the possibility of increasing tolls to raise money for roads.

"There are other ways of funding projects besides raising taxes," Kilgore said.

Kaine also has said his transportation proposals would encourage better land-use planning.

The developing proposals illustrate the importance the transportation issue will have for both gubernatorial platforms next year, lobbyists and lawmakers said.

Two years ago, improving Virginia's transportation system was the hottest issue in state politics. But after referendums to increase taxes for transportation failed in Hampton Roads and Northern Virginia in 2002, the coalition of public and private interests that backed them became disheartened.

In the spring, state leaders raised sales and other taxes by $1.5 billion to increase funding for schools, public safety and health care, but not for transportation. Meanwhile, the state's transportation budget has diminished, and planned projects have been cut.

"Transportation will be the biggest issue that the next governor and the legislature will have to face when they are sworn in January 2006," Kaine said.

Indeed, on Tuesday a group of GOP delegates suggested raising money for projects by borrowing against insurance premium receipts and future surpluses. Opponents of the plan said it hinges on the same sort of borrow-now-pay-later mentality that got the state into its recent fiscal difficulties.

The legislature's most powerful lawmakers, Sen. John H. Chichester and House Speaker William J. Howell, both Stafford County Republicans, have intimated that they, too, are developing transportation funding plans.

Gov. Mark R. Warner (D) has said he is working on a plan, while leading Democrats support raising gas taxes and fees to fund projects. Environmental leaders plan to hold a conference Saturday to talk about their approach to solving transportation problems.

Many of the state's business interests said in interviews this week that they still consider increasing the gas tax an option. The tax was last raised 18 years ago.

"It's similar to a user fee," said Steve Haner, the spokesman for the Virginia Chamber of Commerce.

Other lobbyists said the public needs to be informed about the need for transportation funding, whether through a gas tax increase or other measures.

The Virginia Road and Transportation Builders Association, in concert with local business groups, is beginning an advertising effort it said would explain the situation Virginia finds itself in regarding road building and traffic congestion.

"One of the most important things about this issue is trying to educate people who drive our state roads that there is a need," said Richard Daugherity, the group's executive vice president. "We're not ready to endorse any plan now . . . but at least people are talking about long-term solutions."

Attorney General Jerry W. Kilgore said he would look at "other ways of funding projects besides raising taxes," including the possibility of increasing tolls to help pay for road construction. Lt. Gov. Timothy M. Kaine said state government needs "to make sure that money designated for transportation goes to transportation," an area he said has created "a credibility problem."