Little by little, the realiability of Metro's subway is getting better and better.

A study of Metro's operations logs shows that, on the average, an increasing percentage of scheduled subway trains actually are completing their runs. The improvement has been marked on the Blue Line from National Airport to Stadium-Armory, which opened July 1.

In that first horrible month, only 79.8 per cent of the scheduled Blue Line trains actually were dispatched on an average day. Through the first three weeks of OCtober, that average had jumped to 95 per cent.

People do not ride average trains, however, they ride real ones and when the trains do not show up, people complain. Charles Fizer, who has the unpleasant job of supervising Metro's complaint center, said yesterday that complaints definitely are down, although he does not have hard statistics.

"I went donwstairs Friday and congratulated Tony," said Fizer. "It was the first time I had seen him in a long time when the purpose was to congratulate him."

"Tony" is ANthony J. Stefanac, who is in charge of running trains for Metro. He is too cautious a man to declare victory. "I would say last week was the best week we have had," said Stafanac, "until Friday evening . . ." His voice trailed off.

Friday evening, a train broke down in the Foggy Bottom station of the peak of the rush hour and fouled things up for 25 minutes. It was the first major rush-hour delay in more than a week. In July and early August, such delays happened almost daily.

It will be months before a legitimate analysis can be made of exactly how well the subway is working and what effect it is having on the travel habits of Washington area commuters.

nonetheless, the subway appears to have attracted a solid core of about 130,000 riders daily. Although that is well below some projections for riderating, it is only 10,000 a day short of what San Francisco's Bay Area Rapid Transit carries on a 70-mile system.

Furthermore an early look at a recent bus ridership survey appears to indicate that the number or bus riders has remained fairly stable over the past few months despite great changes in Metrobus schedules.

More than 400 bus routes were realigned or curtailed after the Blue Line opened to change the bus system from a long-haul through service to a feeder for the rail. Still more changes are scheduled for February, when the Red Line is extended from Rhode Island Avenue to Silver Spring.

The result has been a forced change in travel habits developed over years for thousands of Metro commuters. Metro did not make it any easier by adopting a Byzantine fare arrangement that means people pay different fares for rides of equivalent distance depending on when they live and makes difficult the process of transferring from bus to train and back again.

The fare structure was born of politics. The problems with the trains are mechanical and have been solved more easily. Erich Vogel, who is in charge of maintenance for Metro, said can use and only 136 are needed to provide the scheduled service.

All doors on all cars have been re-adjusted once and are undergoing a second fine-tuning. Sticking doors have been blamed for a number of delays, because if the doors stick open, the train will not move.

Six cars a day are getting a major brake system check and several corrections are being made in the brake system. Brakes have been the leading cause of recent train trouble. None of the brake problems is safety related.

Perhaps the most important factor in the improvement of Metro's reliability is that its personnel - supervisors, train operators and mechanics - are all learning their jobs. Metro went over night from a 5-mile system carrying 30,000 people a day to a 17-mile system carrying 130,000 people a day to a 17-mile break system carrying 130,000 and had to break in dozens of new people at the same time.

"The operators are able to get out of their problems a littel faster than they were," Stefanac said. Vogel said his mechanics also have improved as they have learned about the equipment on which they work.

While train reliability has been the most obvious Metro problem, there have been other irritants to regular riders: balky escalators and malfunctioning automatic fare-collecting equipment.

Metro General Manager Theodore Lutz has assigned people to work specifically on both problems and there has been some apparent improvement, although there is no objective gauge. More fare gates have been approved for several important stations uschas Farragut West, Rosslyn and the Pentagon, and Lutz recently recommended that even more fare equipmetn be installed at key points.The theory is that if there is enough extra equipment, the breakdown of a single machine will not be critical.