Ridership on Metro's combined bus and subway system continued to show strong gains through the first quarter of this year, Metro General Manager Richard S. Page said yesterday.

The quarterly ridership report showed that 14 percent more people rode public transit this March than in March 1979 and 36 percent more than in March 1978. On an average weekday this March, a total of 633,021 transit trips were made on Metro.

The statistics show that Metro, like other transit systems around the country, is showing steady month-to-month increases. Metro did not retain all the new riders it captured during the height of the gasoline shortage last summer, but a substantial number still were with the transit system.

Part of the increase in ridership from March to March is attributable to the opening of the new Orange Line subway segment between Rosslyn and Ballston in Arlington County, Page said in his report. That has contributed more riders to the subway sytem and stimulated ridership on bus lines that feed the Ballston station.

The subway continues to attract more and more riders, and during the last week of March had its highest-ever weekend average of 317,964.

Bus ridership also is increasing throughout the system. Metro reported that there was a 19 percent jump in bus ridership from March to March, including trips that fed the subway system, but a 13 percent increase in trips that involved only the bus.

Page also told the Metro board yesterday that the performance of Farecard, the automated fare collecting system used on the subway system, has improved in recent months.

Farecard vending machines at selected stations were available 91.1 percent of the time in April, as compared with 81.9 percent of the time last June. Metro's goal is 95 percent.

Furthermore, Page said, a special modification that Farecard manufacturer Cubic Western Data is trying to sell Metro does not appear to have higher reliability at the one station where it is used -- Farragut West. There, vending machines have been available 98 percent of the time; gates have been available 94.3 percent of the time, and Addfare machines 99.7 percent of the time.

Page is planning a recommendation sometime soon on whether to continue with the Farecard system or change to another fare-collecting method.