Arlington will install 25 bicycle racks this summer at each of its new Metro subway stations, except National Airport, to encourage bicycle-Metro commuting in Northern Virginia.

Bicycle lockers also will be installed at five District Metro subway stations this summer and will go into Montgomery County's new Silver Spring subway station when it opens this fall. Montgomery also will put lockers and bike racks near Metrobus stops at four Montgomery County shopping centers.

If the bike racks and lockers are successful, as they have been throughout San Francisco's BART subway system, they will be installed at most Alexandria, Arlington and Fairfax County subway stations as they open in the next half dozen years.

But bicyclists should not plan on pedaling to National Airport, even though the popular George Washington Memorial Parkway bike trail skirts the airport, because there are no current plans to put bike racks or lockers there.

"We're looking into it now . . . we'd like to see bike lockers at National. In fact, we'd like to see bike lockers and racks all over the place, at every Metro station, in shopping centers, parking lots and office buildings," says Metro's senior transportation planner, Mark Akins.

"But Metro doesn't have any money for bike racks so it's up to local jurisdictions and to the FAA (Federal Aviation Administration) at National to install them." The FAA has no bicycle facilities on the drawing board for the airport.

About 1,900 Arlington residents now commute to work on bicycles, and the county is predicted to be the fastest-growing bicycling community in the Washington area. About 4,400 commuters are expected to bike to work daily in fair weather by 1985, according to a regional bicycle use study now being completed for Metro and the Metropolitan Washington Council of Governments.

However, over the next eight years commuting by bicycle, either to Metro stations or all the way to work, will increase relatively little in the Washington area as a whole, the study says, because most local governments are cutting back on building bikeways.

Protected bikeways and safe storage facilities are considered crucial to any growth in bicycling here, especially commuter cycling, the study concluded after widespread interviews at area households, offices and with many of the estimated 30,000 commuters who now bike to work regularly in good weather.

The Washington area will have about 53,000 bike commuters by 1985, but could have up to three times that many if additional bikeways and safe storage facilities are provided, the study says. The two-year, $35,000 study estimates that about 590,000 bike trips are made in the Washington area on a weekday and more on weekends, and that this will increase to about 890,000 trips a day by 1985. Most of the trips are by children, however.

The study says that the Northern Virginia Metro stations expected to attract the most bicycle commuters by 1985, even without any new bikeways, are Glebe Road in Alexandria, which may have as many as 450 bikers a day. Alexandria's Braddock Road Station and Arlington's Pentagon City station, each with as many as 250 cyclists a day.

Arlington is installing racks but not steel lockers - which have proven popular in the San Francisco area - because there is insufficient space all the six stations opening in July, says assistant county planner John McMillan.

The lockers, which will completely enclose bicycles, will probably be rented at the same $5 a month rate that BART charges. Most bike racks will be free, but the District also is planning to put 100 parking, meter bike racks in downtown Washington, which will be coin-key operated for about 25 cents a day. The meter racks, which hold one bike per meter, also are popular in California.

Metro also is considering permitting bicycles on subways, as BART now does in non-rush hours. However, Metro's senior transportation planner, Mark Akins, says that appears unlikely because so many subway stations have long escalators where bikes could pose hazards. The Arlington stations will be easier for bicyclists to get to because the county is extending existing bike trails on Rte. 50 to Arlington Cemetery and Memorial Bridge.

Neither Alexandria nor Fairfax County has set aside any funds to expand bikeways this year or next year. However, the Northern Virginia Regional Park Authority hopes to create a 42-mile bike trail from I-95 to the Blue Ridge Mountains along the Washington and Old Dominion Railroad right-of-way, no owned by the Virginia Electric Power Co. Purchase of the scenic route, which could become one of the Washington area's most popular bike trails, will go before Northern Virginia voters in a park bond referendum June 14.