The new levy was supposed to relieve homeowners burdened with property taxes, and a lot of arms were twisted to get it passed. But five months after the Virginia General Assembly imposed a regional gasoline tax on Northern Virginia to raise money for Metro, it appears that relief will be millions of dollars less than promised.

"Don't shoot the bearer of bad tidings," said Steve Roberts, a Virginia transportation official who reported to a gathering of Northern Virginia politicians that the tax they shed so much blood over is generating 20 percent less money than anticipated.

The bad news for public transportation and the homeowners whose taxes have been subsidizing it can be blamed, ironically, on Northern Virginia car owners for not driving enough. Gasoline sales, on which the new 2 percent tax depends, have fallen well below projections.

When the gasoline tax took effect in July in Fairfax and Arlington counties and the cities of Fairfax, Falls Church and Alexandria, state tax wizards projected the area's take would be $11 million the first year. Those officials are now expecting revenues of $8.7 million -- and say the localities will get that much only if the price of gasoline rises another six or seven cents in the next six months.

That's just what worries some Northern Virginia officials. "It appears the more gasoline costs, the less it's going to be used," said Joe Alexander, a Fairfax County supervisor, during a two-day Metro conference near Warrenton last week to mull over and, periodically, to moan about spiraling subway costs. "Somewhere down the line," Alexander said, "we may have to find some other source of revenue."

Officials with the Northern Virginia Transportation Commission (NVTC), which serves as regional representative and local battleground for the five Virginia jurisdictions traversed by Metro subways and buses, list a number of reasons for the tax shortfall. Included is the suspicion that residents of the area are driving into counties without the tax to buy gasoline.

Robert Calhoun, vice mayor of Alexandria and chairman of the NVTC, admitted during the Warrenton conference that he has, on occasion, done that, crossing into Loudoun County to fill lup. "I know it's not patriotic," said Calhoun. "But it's cheaper."

Among those hurt by the tax shortfall are homeowners whose real estate taxes have provided the bulk of Northern Virginia's subsidy to the Metro system. A provision of the gasoline tax mandated that for every dollar the new tax brought in, the localities must cut a dollar from real estate revenues. n

But with real estate assessments in the area still rising by an estimated 14 percent annually, homeowners throughout Northern Virginia will pay more in real estate taxes this year than last. Because of the tax shortfall, officials say that increase may be only a few pennies less than it would have been without the gasoline tax.

"Anything we get from the gasoline tax is some relief," said Del. Warren Stambaugh (D-Arlington) who sponsored the gasoline tax bill in the General Assembly. "If revenues come up lower than expected, it just means the burden (on the homeowner) doesn't get shifted as much."

Earlier this year, Stambaugh shepherded the gasoline tax through a particularly stormy session of the General Assembly, a body which traditionally has been hostile to Northern Virginia efforts for Metro. For a time Stambaugh's bill appeared on a collision course with a separate statewide gasoline tax being pushed by Virginia's Gov. John N. Dalton.

After a week of wheeling, dealing and what Stambaugh called "a lot of pretty blatant arm-twisting," the General Assembly passed both a compromise version of Dalton's statewide tax and Stambaugh's tax, which calls for a 2 percent sales tax on gasoline sales in Northern Virginia in 1980-82 and an additional 2 percent tax in 1982-84.

Stambaugh's bill passed by just one vote and was supported by only seven of Northern Virginia's 19 delegates.Most of that opposition came from Fairfax County Republican delegates who claimed their automobile-dominated county would pay more than its fair share of the gasoline tax.

"We're ramming it down their throats," said Del. Warren Barry (R-Fairfax) who protested that the tax should be collected by localities rather than the state. Barry later called passage of the gasoline tax the "rape of Fairfax."

The most strident opponent of the gasoline tax continues to be John F. Herrity, the Republican chairman of Fairfax County's Board of Supervisors. Herrity argues that his county will provide 60 percent of the tax revenue, but under a formula approved by NVTC, will be credited with just 50 percent of the total. "I think Fairfax County is getting ripped off," said Herrity last week. "All I want is our fair share."

Officials in Fairfax County also oppose the allocation formula developed by the region. John Perrin, a Fairfax City Council member and the NVTC's secretary-treasurer, claims his city will be credited with only about 10 percent of the revenues collected in the city, which has an "inordinate number of gasoline stations."

David Erion, executive director of NVTC, which is made up of representatives from all five jurisdictions, said this week that there are no figures to show where gasoline tax revenues come from.

State Del. Vincent F. Callahan (R-Fairfax) has promised to seek a revision of the gasoline tax formula when the General Assembly meets next month. But even opponents of the gasoline tax concede it is unlikely the state legislature will reconsider it after the furor that accompanied its passage.

"We'd have to really weigh the thing to see whether we want to burden the General Assembly with another battle," said Barry, an opponent of the tax.

During an NVTC caucus at last week's Metro conference, Northern Virginia legislators agreed that opening the gasoline tax to further debate in Richmond could endanger the concept of any regional tax. "At this point the climate is just not right to look at anything else," said Fairfax supervisor Marie Travesky, who characterized the gasoline tax revenue as "nothing more than a pittance."

"If we bring this up again, there are plenty of people in Richmond who are going to try and kill it," said Travesky. "What we're set on doing is preserving the little bit we have."