Half-fare farecards for elderly and handicapped patrons of the Metro rail system are now being sold in $2 denominations. They were previously available in $4 denominations.

In announcing the change, Metro general manager Ted Lutz also said two more sakes outlets for elderly and handicapped forecards have been added for a total of 14. The new locations are the treasure's office at Alexandria City Hall and the Community Credit Service at 1311 Rhode Island Ave. NE.

Until Metro rail service is extended in future years beyond the present 18 miles, the farecards, worth $8 of train rides, often have value remaining at the 19th printout line. The new $2 denomination eliminates that problem and simplifies use for the elderly and handicapped. Until Metro rail service is extended and trips are longer, the $2 card will run out value before the 20th printout line. If the value remaining on the card is less a single trip it can be used as credit when purchasing a new card.

To purchase discount farecards, senior citizens must present a Metro senior citizen identification card. Those are available at any of the 92 public libraries in the Washington metropolitan area, or at Metro outlets. For more information call 637-1179.

Handicapped people must show a Metro handicapped identifiction card to purchase the discount farecards. Application forms are available at Metro outlets. They can also be mailed out from Metro's Handicapped Service Unit at 637-1245 or 1246. Applications must be completed by a licensed physician.

In addition to the new sales outlets, other locations include: Metro Headquarters, 600 Fifth St. NW; 1422 New York Ave. MW; 10th Street and Pennsylvania Avenue NW; Pentagon Concourse, B-5 stairway; Metro mobile sales van at L'Enfant Plaza on Mondays, 16th and K Streests on Tuesdays and Fridays, Crystal City on Wednesday, Interior Department on Thursday; and seven Metrobus divisions in the District, Northern Virginia and Maryland.