At what point do Metro's regular riders say, "This is where we get off"--and start heading for their cars? (a) when fares go up; (b) when service deteriorates; (c) when local taxes are raised to subsidize transit; (d) when gasoline and parking prices appear to be stabilizing; or (e) when any or all of the above has happened. Any of these circumstances can cause Metro ridership to decline. Worse yet, "all of the above" is happening right now.

The latest Metro math is grim: an operating budget just approved by the Metro board calls for $337 million--and that means reaching into the public's pockets, one way or another. One way is with a fare increase of a nickel or more come Jan. 1, which would be the fourth rise in 2 1/2 years. Another way is with higher subsidy payments from the participating state and local governments, and therein lie the makings of a political kamikaze mission for the elected board members.

If bus or subway service gets much worse, off will go still more riders--reluctantly, perhaps, but battle-weary from transit breakdowns, no-show buses, ever-changing routes and schedules, multiple transfer points and everything else that comes together to spell inconvenience. While localities may be able to help by taking over additional Metro bus routes more economically, as Ride-On has done in Montgomery County, there are limits to these economies.

However depressing these options may be, Metro has survived worse financial perils. A combination of moves--coupled with some serious thought to a reorganization of the regional management--is critical:

Slightly higher fares may be unavoidable, but if they can be combined with a more uniform, understandable fare structure and better service, riders will adjust with fewer defections.

State and local governments should be convened by the Metro board to agree as specifically as possible on a regional tax plan that would earmark revenues for Metro without all the yearly political agonizing.

Metro salaries should be disconnected from direct, tie-ins with the full cost-of-living index, which has resulted in skyrocketing labor costs.

Changes in the labor cost-of-living clause, as well as any other restructuring of Metro's management as spelled out in the original compact, require word- for-word agreement among Congress, the Maryland and Virginia legislatures and the D.C. Council. But as staff writer Douglas B. Feaver noted in an Outlook article Sunday, the management of Metro needs overhauling to reflect the increasing roles of the state governments in the financing--and thus the policies--of the regional transit system. Govs. Hughes and Robb and Mayor Barry could--should --start this process right away.