SO MANY DO-OR-DIE hours have been squeaked by safely in the financial history of the subway system that it's difficult to recognize yet another moment of decision for responsible officials, but one is coming -- this afternoon. In no uncertain terms, the federal partners have notified their local colleagues that it's time to settle a big debt or lose critical construction money. The Metro board has scheduled a special meeting, and unless the members vote to sign a painstakingly negotiated agreement to settle a $1-billion debt, it will cost them $275 million that the federal government must obligate either here or somewhere else by the end of the month.

The warning from the U.S. Department of Transportation is justified. The agreement would resolve the biggest issue separating the federal and local governments. The debt stems from $1 billion in bonds that Congress permitted Metro to sell in its early years; an agreement reached in principle nearly two years ago calls for the federal government to pay two-thirds of the bond cost and Metro the rest. But when the federal government sought written guarantees from the eight local governments participating in Metro, the governments balked, claiming the debt was not theirs, but Metro's.

After that dodge, the latest compromise was worked out. Now there's no freedom to back out; it is up to Metro -- and that means the local governments, too -- to do what has been required.