AFTER A STRING of perils and a happy ending in Richmond, the critical search for state support of Metro in Annapolis turned out to be a legislative piece of cake. To the delight of most Maryland legislators, the effort to pin down money for Metro was short and sweet, ending not with a bang but a surplus. Whatever threats existed when the Maryland lawmakers convened went away when the latest revision of constantly revised revenue estimates pushed the size of the surplus well above $300 million. That was enough for Gov. Harry Hughes to drop a proposal that would have raised car registration fees to cover the Maryland transit ante. So does that do it for now?

Sorry, but all passengers should transfer at this juncture to the District of Columbia -- where the next trip to the well is scheduled. Since the two states have done their part to comply with a federal mandate to find "stable and reliable" sources of money for the transit system, the spotlight is on the District, where Mayor Marion Barry has repeatedly guaranteed that he will comply before a deadline of Sept. 30. That's fine, except for that hollow sound every time somebody taps the city's coffers these days. This financial discomfort points up another unpleasant move that the District government had best consider a little more seriously than it has up to now: higher transit fares -- not just nickels and dimes every decade, but increases beyond those now being proposed for bus travel in the city.

Suburban officials, acutely sensitive to yelps from property owners about real estate taxes, have long recognized and advocated fares that have some relationship to operating costs and -- one shudders -- inflation. But their counterparts in the District have been reluctant to do much about fares, preferring to point to the social services aspects of mass transit and the number of poor people in the city. The poor do need help in the form of subsidies for mass transit, but what about other District bus and subway riders who could afford to chip in a bit more each day as the costs of driving their cars continue to soar?

The Maryland measures just approved contain a requirement that in Montgomery and Prince George's counties, the farebox revenues make up half the system's operating deficit. Though one may argue about the ideal percentage, this kind of requirement does provide an incentive for the two county governments to maintain realistic fares. In the District, where there is no state government to provide that spur, it takes that much more political courage to increase fares. But sound financial policy demands precisely this kind of move from a mayor and council farsighted enough to act before it's too late.