THANKS TO some solid, bipartisan work by Reps. Frank Wolf of Virginia and Steny Hoyer of Maryland, construction of Greater Washington's Metrorail system -- particularly the all-important Green Line connecting some of the center city's least mobile residents with the rest of the region -- has won critical new support in the House. On Thursday, a subcommittee turned aside budget-cutting requests from the Reagan administration and voted for a reasonable appropriation to continue building the subway network in the city and suburbs as well. The proposed allocation for the fiscal year that starts on Oct. 1 is the same amount that Metro got for this year. There are still more votes to be taken in the House -- and then action by the Senate, where the going may not be so great, but congressional approval of the subcommittee's recommendation would avoid expensive delays in the planned construction schedule and complex recalculations of state and local financial support.

Those state and local commitments have been met every time throughout the years -- an important fact that more and more members of Congress have recognized as solid grounds for continuing timely federal support. In the Senate, Virginia's John Warner and Paul Trible and Maryland's Paul Sarbanes and Barbara Mikulski have been working to generate this understanding, and to emphasize that popular support for building the entire regional subway system has not waned a bit.

Just as durable is the original idea of this subway project, envisioned decades ago as a cooperative venture of the federal, state and local governments. Today, visitors to the capital city as well as residents here continue to use the system in growing numbers every year. For those people around the region who have been paying and waiting patiently for construction of the lines into their neighborhoods, fairness does call for an orderly pace toward the full 103-mile system. Congressional support now can keep things moving.