RESPONDING WELL to a put-up-and-so-will-we challenge from Transportation Secretary Brock Adams, local leaders throughout the Washington area have agreed unanimously to seek taxes specifically dedicated to help pay for Metro. This significant resolution came at the conclusion of an impressive weekend conference on Metro attended by about 200 people, including elected offcials from all area governments, state legislators, congressional staffers and federal representatives.Though the action has no legal standing, it represents an important reaffirmation by the region's leaders that they are committed to completion of the Metro rail system and will find ways to raise and earmark money for running the trains and buses.

The agreement has been carefully worded to accommodate some strong intraregional differences over precisely how the revenues should be raised.

While a single region-wide tax of some sort might seem best, officials recognized the political impossibility of achieving any such arrangement.As many representatives pointed out, anything resembling a uniform "regional tax" or regional taxing authority would not be looked upon fondly in the state legislatures of Maryland and Virginia.

Instead, the efforts to build a local kitty for Metro will differ in Annapolis and Richmond. Maryland representatives are talking about earnmaking I percent of Maryland's 5 percent general sales tax for the state's transportation trust fund; it could be spent in many different ways around the state-transit, roads, railroads, etc-and would not involve an increase in the tax rate. Members of the Northern Virginia delegation to the General Assembly are gearing up to try again for permission form Richmond to raise the sales tax in Northern Virginia from 4 percent to 5 percent and to dedicate the additional percentage point to transportation projects. There also would be a penny-for-penny decrease in the property tax rates charged Northern Virginia homeowners and businesses.

On this kind of tax matter, it's interesting to note that the District of Columbia now enjoys more local autonomy than its suburban counterparts. The D.C. government is free to tap a variety of sources, and officials have not reached any firm conclusion about which direction to take.

Still other questions produced strong suburban-city differences, most notably how fares should relate to costs. Sururban jurisdictions have called for fares to increase in relation to the Consumer Price Index; District officials have opposed this method but did agree to consider some kind of fare-adjustment formula based on the ability of individuals to pay. However this is eventually resolved, the more important step taken last weekend was the region's statement of determination to complete the subway system and to accept the terms for impressive help from Mr. Adams and the federal government. The spotlights now shift to Annapolis and Richmond-where the understanding and support of the state legislators will be crucial.