Starting tonight, Metro will stay open an extra hour on Friday and Saturday nights, running trains until 1 a.m. instead of midnight. The move, which marks the first time Metro has extended evening hours since 1978, is an eight-month test of late-night service.

Running trains until 1 a.m. is expected to generate 4,600 new trips each night, Metro officials said.

After six months, the Metro board of directors will evaluate the ridership figures and the impact of longer hours on daily service and will consider extending the weekend closing time to 2 a.m.

For years, Washington has had the earliest closing time of the nation's largest transit systems, drawing complaints from residents and visitors. A recent campaign to extend subway service attracted unlikely allies that included businesses and environmentalists, Mothers Against Drunk Driving and rock radio listeners. Clubgoers in Adams-Morgan and the U Street area joined with elected leaders in the District and Montgomery and Prince George's counties in supporting the change.

Opponents of extended hours worry that it will reduce the "maintenance window"--the early-morning hours when the trains stop running and tracks can be shut down for repair work.

Although Metro's official weekend closing time will be 1 a.m., the time of the last train will differ from one station to another, so passengers should check the "last train" schedules posted at each subway station. The last train will leave a station as early as 12:30 a.m. or as late as 1:38 a.m., depending on how close the station is to the end of the line, Metro spokesman Ray Feldmann said.

A complete listing of "last train" departure times is available at www.wmata.com, Metro's Web site. Passengers can also call Metro's customer information line at 202-637-7000 or TDD at 202-638-3780.

Here are the departure times for the last train at some of the more popular nighttime stations:

* Woodley Park-Zoo/Adams-Morgan: 1:12 a.m. for Shady Grove and 12:58 a.m. for Glenmont.

* U Street-Cardozo: 12:50 a.m. for Anacostia and 1:21 a.m. for Greenbelt.

* Dupont Circle: 1:10 a.m. for Shady Grove and 1 a.m. for Glenmont.

* Foggy Bottom-GWU: 1 a.m. for Addison Road and 1:10 a.m. for Franconia-Springfield.

* Rosslyn: 1:13 a.m. for Vienna/Fairfax, 1:16 a.m. for Franconia-Springfield and 12:57 a.m. for New Carrollton/Addison Road.

* Clarendon: 12:42 a.m. for New Carrollton, 1:17 a.m. for Vienna/Fairfax.