Northern Virginia is among more than two dozen places across the country where voters will be asked to tax themselves or raise fees to pay for transportation projects, a pattern that is changing the way Americans finance new roads and transit, according to a national study released yesterday.

In recent years, many states have turned away from gas taxes and instead are allowing voters to raise sales taxes or sell bonds to pay for transportation projects, according to the study by the Surface Transportation Policy Project. Of the 41 transportation revenue measures that either have appeared or will appear on ballots this year, only four seek to raise user fees.

Two factors are propelling this shift in transportation financing: State lawmakers and governors are reluctant to raise gasoline taxes, and there are no easily identifiable user fees for public transit projects.

The policy project analyzed five ballot measures in depth, including the Northern Virginia referendum. The results were not complimentary: It found the Northern Virginia plan to be more poorly designed than others.

On Tuesday, voters in nine of the region's jurisdictions will be asked to raise the sales tax a half-cent per dollar to generate more than $5 billion over 20 years for local road and transit projects.

The policy project, a national nonprofit collection of more than 800 planners, community development organizations and advocacy groups, said the ballot question is too vague regarding the way the money would be spent.

"Our bottom line is, it raises more questions than it answers," said James Corless of the policy project. "There's a slug of money that's unaccounted for. There's a project list, but then almost half the funding is not earmarked, and there's an attitude of, 'We'll figure it out when we get to it in the future.' "

Under the terms of the referendum, the proceeds from the cash will be used to issue bonds worth $2.8 billion to finance all or part of 23 generally described projects. The tax is expected to generate an additional $2.2 billion, but its uses are not specified. The expenditures will be decided later by the new Northern Virginia Transportation Authority, made up of local elected officials and appointees.

"This is seen as a significant problem and amounts to a traditional 'trust us' approach that gives voters little assurance of how and where the remainder of their money will be spent," the study says.

Also missing are any performance criteria that tell voters what the measures will do to reduce congestion and improve transit, the study said. Without clear goals, it is difficult for voters to know whether the ballot measure will make a difference, according to the policy project.

John Milliken, a former state transportation secretary and head of the pro-tax Citizens for Better Transportation, said the referendum offers enough details. "We've gone about as far as one can go to specify," he said.

The new transportation authority is charged with developing performance standards at a later date, Milliken said.

The study also takes issue with generating revenue from an increase in the sales tax as opposed to an increase in the state gasoline tax or tolls. Financing transportation projects with an increase in the sales tax disproportionately affects low-income people because they spend a larger share of their budget on the tax than wealthier families, the study said.

A more just approach would be to increase the gas tax and raise or create more tolls so that motorists who use the road network are paying for new roads, the study said. This is often referred to as a "user fee." That would also force commercial trucks, which travel Virginia roadways during long hauls up and down the Eastern Seaboard, to share the burden.

"Politically, legislators don't want to raise the gas tax," said Martin Wachs, who directs the Institute of Transportation Studies at the University of California at Berkeley and is writing a book about transportation financing. "They decide not to raise taxes. Instead, they decide to tell the voters to do it. It's an act of political cowardice."

The study found that over the past 35 years, the federal gas tax has increased often enough that it has outpaced inflation, but state gas taxes have stagnated.

In Virginia, for example, the state gas tax in 1957 was 6 cents per gallon. Adjusted for inflation, that figure today would be 32.5 cents. But the actual tax is much less -- 17.5 cents per gallon.

In addition to failing to raise the state gas tax to keep up with inflation, Virginia legislators also rolled back the state car tax, further reducing the amount it collects for transportation projects.

Milliken said an increase in the local sales tax is not unfair to people with low or fixed incomes because food and drugs would be exempt from the tax.

"Regressive is a relative term," he said. "A gas tax is more regressive than a sales tax that does not apply to food and drugs. If one is going to get around in the region, you are going to pay a gas tax because you don't have much choice."

Stewart Schwartz, head of a slow-growth coalition that opposes the ballot measure, said the policy project's study confirms many of the claims of tax opponents.

"The $2.2 billion in unallocated cash -- there's no information about what projects it would be earmarked for, and what priority these projects would take," Schwartz said. "It doesn't have any performance criteria and has not been evaluated in any way for how effective it could be in reducing traffic."

Indeed, most transportation initiatives do not clear congestion, Wachs said.

"Building facilities doesn't really alleviate congestion at all," he said. "The reason one would build is to increase the capability of people to move about. But eventually population growth will cause traffic to grow. Any measure would probably alleviate congestion temporarily, but it will readjust over time."

John Milliken, leader of the pro-tax Citizens for Better Transportation, speaks at a campaign kickoff rally. With him is Margaret G. Vanderhye of McLean.