THE TIMING WAS more predictable than the arrival of the next Green Line train: This week Metrogrousing among riders rose in tandem with the fares. It's still too early and probably the wrong season to gauge the number of people who hit the point of no return to transit because of higher riding and parking fees, and now shorter late-night trains. But hopping into cars just became more attractive to many families as well as commuters. Whether it's the round-tripper on rail from Vienna to downtown Washington at more than $7 a day or the family of four in the District paying more than $13 for an in-town dinner outing starting at rush-hour rates, more than a few people will decide that this is where they get off.

Transit officials expect about 14,000 rail passengers, out of the current average of 670,000, and about 3,200 bus riders, out of 550,000, to stop taking public transportation because of the higher costs. The inevitable result will be worse traffic. How much more can Metro expect to collect from fares? Will the board of directors be looking at yet another set of increases next year? Cost-cutting measures may help a little, but there is no question that more cash will be needed for operating as well as capital costs. Officials estimate that Metro will need about $1.5 billion over the next six years to repair and replace rail cars, buses and other equipment, to say nothing of improving security. Rising operating costs have led to a projected $23.4 million deficit in the system's $940 million operating budget.

Metro officials note that the latest increase is only the second time in nine years that fares have been raised. But the last boost was only a year ago. When fares were frozen, local governments increased their subsidies; when Metro raised fares last year, those governments not only didn't want to pay higher subsidies, they also wanted money back from the higher fares. At least for this latest round, they will not be taking that money back.

"We cannot sustain the high growth in subsidies," says Robert J. Smith, appointed by Maryland Gov. Robert L. Ehrlich Jr. to the Metro board and currently serving as its chairman. "The reality is, the system is crowded and has a lot of users, and people have to be willing to pay fees to fund the system." But Metro passengers already pay a higher share of the cost of a ride than do transit riders elsewhere. Metro says its bus and rail passengers pay 57 percent; the national average is 37 percent. Rail riders are paying 76 percent of the costs of their rides -- one of the highest shares in the country.

Missing in this mix is a dedicated source of revenue for Metro, which other systems depend on. Local and state governments used to talk about this and then not do anything about it. Today, they don't even talk about it.