The Washington Metro is within a few months of being able to demostrate its ability to change the face of the metropolitan area much as the Capital Beltway did after it was completed 13 years ago.

The almost daily turned over Metro's financial problems makes it easy to lose sight of the fact that by the end of 1978 trains will be operating on 2 3/4 miles of track throughout the metropolitan area.

It will be possible to take the subway from the Beltway at New Corrollton to National Airport, or from Silver Spring to RFK Stadium. For the the first time, there will be significant track meleage in Maryland as well as in the District of Columbia and Virginia.

And the system that was designed and sold in the late 1960s as a regional unifier and a stimulus to more efficient development and redevelopment will begin more obviously to fulfill that .

There is substantial evidence that Metro is already having an impact on business and financial decisions because of its ability to move people quickly and painlessly to areas that were becoming increasingly difficult to reach by automobile.

For example:

Major redevelopment projects have been annouced or are underway on the southwest corner of Thomas Circle and in the block bounded by 14th, 15th, E and F Sts. NW. Both locations are within easy walking distance of Metro stations. Both are in the older downtown area that developers have avoided in recent years.

Arlington County has seen a burst of building activity in the form of apartments, townhouses and businesses in the area immediately southeast of the Pentagon City Metro Station. That station, which appeared to be built in a desolate wasteland, promises to be the center of a major urban neighborhood.

Merchants in Crystal City and Rosslyn have told the Arlington Chamber of Commerce that their sales have increased dramatically since the July 1 opening of the Blue Line, which brought Metro passengers to their front doors.

Major industrial and warehousing centers are planned or under construction near the New Corrollton station, which is scheduled to open on the fall. That station will tie Metro and Amtrak together at a point easily accessible from both the John Hansen Highway and the Beltway.

Woodward and Lothrop, the department store with both the good fortune to be located on top of the Metro Center Station and the good sense to buy direct access to Metro through its basement, reports a large increase in customers at that downtown location.

In the short time that Metro has been operating more than a minimum system, it has demostrated a steadily increasing ability to attract and hold customers. When the Blue Line opened in July, the trains were plagued with operational difficulties. Getting struck on Metro became an acceptable excuse for being late to work.

But in the past three months, Metro seems to have licked its mechanical problems. Weekly reports show that more than 95 per cent of Metro's trains are operating on schedule. A more perceptive indicator is the fact that ridership continues to climb steadily. Daily average subway ridership was about 132,000 in early December with several day's figures exceeding 140,000.

Many of those riders can be presumed to be subway-only users because Metro's total bus and subway ridership dropped during the morning and the evening rush hours after the massive realignment of bus routes that followed the opening of the Blue Line. A bus fare increase in the District of Columbia contributed to that drop.

Subway-only users, particularly Metro's already famous lunch bunch, can be further presumed to be shoppers.

The Metro has given new mobility to Washington's relatively high-paid work forced and made it possible to negotiate the vast downtown area during the lunch period.

Metro is also a significant economic force in its own right. The Washington Metropolitan Area Transit Authority, Metro's formal name, employs 6,000 people and has an annual payroll of $102 million. That includes bus drivers, mechanics, train operators, station attendants and general manager Theodore Lutz.

Furthermore, Metro's construction program is the largest public works project underway in the United States. Last year it employed a monthly average of 4,150 people in this area. Construction expenditures for calendar 1977 alone were $328 million - $150 million of it in wages.

Midway through December, Metro's construction program had cost $1.9 billion (the total planned 100-mile system is now estimated to cost more than $5 billion).

Metro is a good customer for other area businesses. In the last year it bought $100,000 in office supplies, leased property for $1.1 million and purchased $4.9 million in services from printing to maintenance.

These are some of the things the Federal City Council began to discover when it decided to take a close look at Metro and its problems. The council, a non-profit organization of the most influential business and professional people in the area, came away from that study both impressed with Metro's potential and seriously concerned about its future.

R. Robert Linowes, who served on the council's task force and who is also president of the Metropolitan Washington Board of Trade, said "I think we need (Metro)."

However, Linowed cautioned, the political process of maintaining support, financing the system, and perhaps most importantly, making the land use decisions that will guarantee the system's success, has not kept pace with the construction program.

The financial is in place to complete 60 miles of Metro. Money will probably be found for more than that, although not necessarily for the 100 miles presently on the map.