Once again this weekend, Metro’s aggressive maintenance program is going to affect service on all the lines. The persistence of these scheduled delays was one of the reasons riders reacted with such concern about the transit staff’s proposal to establish a formal standard on the time between trains.

It wasn’t that having a standard was a bad idea, but the standard’s threshold was so low. In the original version, it would have set a minimum of 15 minutes between rush hour trains and 30 minutes between off-peak trains.

A revised version set for approval at Thursday’s Metro board meeting would have set thresholds for normal operations at a maximum of 15 minutes between trains at peak, 20 minutes off-peak service and 25 minutes after 10 p.m.

But the board pulled the item from the agenda this week for further review and discussion. That’s good. I do think having a service standard is a fine idea, but with riders so discouraged about the current state of the service, it would be wrong to glide such negative numbers into formal policy.

The schedule listed below is the type that discourages many people from using transit on weekends, and it has become almost normal. The adoption of a minimum standard would not have changed the actual train schedules, but riders who experience these weekend delays fear the standard is a step in that direction.

All these delays and disruptions apply, as usual, to service between 10 p.m. Friday and the train system’s midnight closing Sunday.

Red Line: Free shuttle buses will replace trains between Grosvenor and Friendship Heights. Medical Center and Bethesda stations will be closed. Trains will operate between Shady Grove and Grosvenor and between Friendship Heights and Glenmont.

On each segment, they will operate every 10 minutes between 9:30 a.m. and 6 p.m. and at regular weekend intervals at other times. But if you’re traveling on the shuttles through the work zone, add half an hour to your normal travel time.

This is the same maintenance disruption that riders experienced last weekend, and it will be repeated the weekend of Aug. 10-12.

Blue Line: Free shuttle buses will replace trains at the Franconia-Springfield and Van Dorn Street stations. Blue Line trains will operate between Largo Town Center and Huntington on their regular weekend schedules.

The buses will operate between Franconia-Springfield, Van Dorn Street and Eisenhower Avenue stations. So if you’re heading south on a Blue Line train, you want to get off at Eisenhower Avenue to pick up the shuttle to Van Dorn Street and Franconia-Springfield.

Using the buses will add about a half hour to your normal travel time. A weekend rider might prefer to park at Huntington rather than Franconia-Springfield.

Orange Line: Trains will share a track between East Falls Church and West Falls Church, and between Stadium-Armory and Cheverly. Throughout the weekend, they are scheduled to leave the ends of the line at Vienna and New Carrollton every 24 minutes.

Between 9 a.m. and 6:30 p.m. Saturday and Sunday, additional trains will operate between Vienna and Stadium-Armory. So on that part of the line, trains should arrive at platforms about every 12 minutes.

Green Line: Trains will share a track between Fort Totten and Prince George’s Plaza. Add about 10 minutes to normal travel times.

Yellow Line: There’s no track work along the Yellow Line, but because of the Green Line work, the Yellow Line trains will end their runs at Mount Vernon Square. Riders who want to go north from there should wait on the same platform for a Green Line train.