For subway riders who find themselves peering anxiously into dark tunnels to see if a train is coming, Metro is mulling over a proposal: a printed, pocket-size timetable.

Advocates say a timetable would be convenient. It would help commuters decide whether to take the subway or drive, they say, and passengers would know if they have time for a quick phone call. On their way home, commuters could figure out if a train would get them in soon enough to catch their bus.

Skeptics counter that trains run too frequently at rush hour to make a timetable useful. They say that a timetable might expose Metro to criticism, especially if trains miss their schedules. Many riders do not want a timetable anyhow, they argue.

After months of review, proponents of a timetable appear to have gained some headway. "Some sort of timetable should be published," said Fairfax County Supervisor Joseph Alexander, who heads a committee of Metro's board of directors that is weighing the issue. He suggested either distributing timetables or posting them in rail stations.

Most other rail systems in the United States already provide timetables for their passengers. Metro distributes timetables for its bus routes. Earlier this year, the transit authority spent $1,630 to survey Metro riders' opinions about publishing a timetable for the Blue, Orange, Red and Yellow lines.

The results of the survey were mixed, officials said, and the issue is still under study.

Two-thirds of those surveyed said they definitely (29 percent) or probably (37 percent) would use a timetable regularly if one were available, while one-third said they definitely (13 percent) or probably (21 percent) would not. Thirty-three percent said a timetable is important, 28 percent said it is unimportant and the others were neutral.

The study was triggered partly by the publication of Metro's rail timetables for the first time by The Washington Post last year. Metro General Manager Carmen E. Turner said then that the authority would look into distributing rail timetables. Since then, train schedules have been revised.

The study, released last summer, said most trains stay close to their schedules, a finding in line with earlier Metro reports. A two-day survey in May found that 76 percent of the trains came within one minute of Metro's schedule, 90 percent within two minutes and 94 percent within three minutes.

But noting that 4 percent were off schedule by four minutes or more, the report warned that publishing a timetable could leave Metro open to complaints.

Metro's reputation for reliable service "undoubtedly benefits" from passengers' "unfamiliarity with train schedules," the report said. With a printed timetable, riders could determine if trains were on schedule and might complain if they were not.

"Failure to meet the published schedule has the potential for tarnishing patron perception of service reliability," the report said. Officials predicted that publishing a timetable could "dramatically increase" complaints.

One advocate of publishing a timetable is Edward A. Daniel, transit services chief for Montgomery County. A printed schedule would help commuters use the Red Line, he said, especially if they are heading for the soon-to-open Shady Grove terminus near Gaithersburg after rush hour, when trains will run at 12-minute intervals.

Ross Capon, executive director of the National Association of Railroad Passengers, also has urged Metro to publish a rail timetable. "I just don't think that Metro does itself a favor by keeping that secret," he said, pointing to the popularity of San Francisco's rail timetables. "BART finds that they go like hot cakes."

Aside from Metro, the New York City subway system is the only big-city rail system in the United States that does not publish a timetable. A spokesman for the New York City Transit Authority said that some form of timetable is expected to be included in a "Guide-A-Ride" display posted in subway stations next year.

A Metro spokesman said Turner now favors publishing a rail timetable if it is possible. Officials said a printed schedule might prove especially helpful at night, when rail service is reduced to intervals of 10 to 15 minutes on some lines and most connecting buses run less frequently.

Officials estimated that Metro would have to print more than 1 million copies a year of the proposed weekday timetable and 500,000 copies of weekend schedules. The annual cost would be $60,000, officials said.