BEFORE THE LEGISLATURES of Maryland and Virginia hit the road this year, motorists in the two states can expect to see new gasoline taxes--and the big question in each capital right now is the same: how much, and for what? The way things have been going in Annapolis and Richmond, the answers will be measures not only of influences within the legislatures but also of each governor-- one currently in the last year of his term and the other in his first. And in neither capital will the ultimate tax measure be enough to address the broad, serious and expensive transportation problems of each state.

In this region, of course, transportation means more than roads. The operative word is spelled M-e-t-r-o, which, any smart lawmaker knows, is a matter of deep, long-green concern to every taxpayer in the suburbs of Greater Washington. It is also, as any veteran lawmaker knows, something less than a burning issue in the minds of constituents from rural areas, where roads are desperately in need of improvements.

At least in Maryland, the financing of Metro is in reasonable enough condition already, with provisions to meet the federal government's requirement of a "stable and reliable" source of money for the transit system in each of the two states as well as in the District. Though Gov. Harry Hughes has seen his original gas-tax proposal cut in half, a compromise that would involve a series of increases starting with 2 cents more a gallon would yield enough to cover the state's most urgently needed highway and road projects.

The story in Virginia is far gloomier. The possibility of serious new financing for Metro is about as "stable and reliable" as Northern Virginia's influence in the House of Delegates--which is to say not much to write home about. The delegates from Northern Virginia have vowed to block any gasoline tax increase that doesn't include money for Metro, but they will need all the influence that Gov. Charles S. Robb can exercise on their behalf-- which is to say too little so far.

Still, Mr. Robb remains optimistic, and says he believes the final version out of Richmond may include Metro money. Certainly it should--and any reasonable lawmaker should recognize that a balanced transportation program in Virginia need not shortchange any section of the state. Legislators who vote to ignore serious mass transit matters are acting irresponsibly in ways that will cost their own tax-paying constituents more in the long run than would a balanced transportation program.