Despite a record fare increase last July, August and September of this year than in the same period a year earlier, the transit authority said yesterday.

Metro's quarterly ridership report says that there was a 1 percent increase in bus and subway riders over the same period in 1979. Average weekday ridership was 627,853, up from 621, 727. A rider who takes both the bus and the subway for one trip is counted once.

Planners were concerned that Metro would show a quarterly drop in ridership for the first time in many years, not only because of the fare increase but also because the period in question was competing with July, August and September of 1979, when Metro had a record 29 percent ridership jump in the midst of the gasoline shortage.

"There is no question that without the fare increase we would have had substantially higher ridership," Metro financial planner Robert Pickett said. "There was enough normal growth in the system to give us another increase, however slight."

The report comes at a time when Metro is considering its second fare increase in six months and service cutbacks on several bus routes throughout the region. Metro riders have turned out in heavy numbers at public hearings over the last week, primarily to protest proposed cuts in bus service but also to question the wisdom of another heavy fare raise.

The ridership report shows there was a slight decrease of 12,475 in total bus ridership that was offset by a 5 percent increase in rail ridership. The subway carried people an average 281,624 times per weekday in the period reported, up from 267,518 trips per day in the quarter a year earlier.

That is partially explained by the fact that the bus network is being reshaped to feed the rail system instead of to stand on its own.But it may also mean that the hefly suburban bus fare increases combined with service that some observers feel has been deterioriating in recent months simply pushed riders back into automobiles or vans. There is substantial evidence that carpooling has increased dramatically in Virginia, along with bus fares.

In other Metro matters yesterday, the Metro board, as expected, approved unanimously the continuation of the Farecard automatic fare-collecting system. u