Metro is now pausing briefly before opening trains doors at each station.

The transit agency has ordered train operators to wait momentarily before opening doors at each stop to "ensure proper operation and to maximize safety," said Metro spokeswoman Caroline Lukas. The wait is reportedly five seconds per stop.

On the Red and Blue lines, which each have 27 stops, an addition of five seconds at each station adds two minutes and 15 seconds for each train to run the length of the line. Even on the Yellow Line, which has the fewest stops, trains would spend 85 seconds longer traveling from end to end under the new directive. That time adds up as trains run back and forth, and could cause other delays especially during rush hour when trains are already closely spaced.

Riders traveling long distances may especially notice the time of the trip creeping upward.

But Metro said it is not going to add time to the schedules. "We are not adjusting schedules for a momentary pause, no," Lukas said.

Metro would not say when the directive began, but riders reported hearing operators warn of the rule as early as Friday.

The agency said the new door protocol is not directly related to any one incident. The transit agency had said it was issuing a safety bulletin about train door openings to all train operators last month after The Washington Examiner reported on a Green Line train's doors opening before it arrived at the Greenbelt station. The train operator was disciplined for opening the doors early.

Metro has taken various safety steps with its doors over the years. The doors used to open automatically, cued by signals communicated by the tracks, then closed by train operators before leaving the stations.

But in 2008, Metro ordered train operators to open the doors, as well, after a series of incidents in which doors opened automatically on the wrong side. Metro blamed electromagnetic interference and said the problem should be fixed by fall 2009.

However, Metro train operators still continue to open and close the doors. The operators also now drive the trains manually since the deadly June 2009 Fort Totten crash, instead of having the trains run automatically by computers. The transit agency has said it hopes to return to automatic train operations at some point, and announced last week it had cleared an important milestone in that quest by having federal investigators approve a safety monitoring tool. But the agency has not publicly said it plans to end manual door opening.