Under Rush Plus, three trains in each direction will be added to the Orange Line and Yellow Line during rush hour. (Ricky Carioti/WASHINGTON POST)

On Monday, Metro will launch Rush Plus, a major service change that transit officials say will improve rush-hour commutes for riders on the Orange and Yellow lines but may lead to longer waits for folks who travel the Blue Line.

With Rush Plus, Metro hopes to clear space in the Rosslyn tunnel for the arrival of the Silver Line and relieve crowding on the Orange Line, where trains between the Court House and Rosslyn stations carry more passengers than anywhere else in the system.

But with fewer trains running on the Blue Line during the same rush-hour spans, Metro officials acknowledge that not all riders will benefit. The loss of trains on the Blue Line has prompted some of the system’s critics to dub the plan “Rush Minus.”

(Live blog: How the first morning of Rush Plus is going)

Rush Plus is one of Metro’s strategies for responding to increased ridership at a time when the transit system lacks the resources to invest in major capital projects. The shift to eight-car trains on some lines is another way Metro has tried to accommodate the growth.

“They really are trying to manage demand on their existing system,” said Ron Kirby, director of transportation planning for the Metropolitan Washington Council of Governments.

The shift is intended to provide more service to stations along the north-south corridor in the District to accommodate job growth in neighborhoods on the city’s east side, such as NoMa.

“Metro is seeing more passengers coming from Northern Virginia who are interested in going to the eastern side of the map and less so to the western side,” Kirby said.

Under Rush Plus, three trains in each direction will be added to the Orange and Yellow lines during rush hour, between 6:30 and 9 a.m. and 3:30 and 6 p.m. Metro says the changes will improve service for about 110,000 riders. “Rush Plus is designed to ease crowding, provide more transfer-free options and, in some cases, faster service, depending on your origin and destination,” Metro spokesman Dan Stessel said.

For Metro’s management and staff, Monday will be a major test — and perhaps the agency’s biggest logistical challenge since the 2009 presidential inauguration. That effort, in which the transit system ran rush-hour service for 15 consecutive hours to accommodate the record crowds, was largely considered a success. In some ways, though, Rush Plus will be even trickier because officials must make it work every weekday.

Part of Rush Plus’s success will rest on the agency’s ability to communicate with its customers — historically not one of Metro’s strengths. The agency has invested an estimated $400,000 in a public-awareness campaign designed to get the word out to the 126,000 commuters who officials say will be affected by the shift.

Metro officials said they don’t expect any major problems but plan to deploy more than 100 additional staffers at key stations.

“We’re going to have a lot of people out there,” said Metro General Manager Richard Sarles.

Stessel said that because most riders commute into the District from the suburbs, officials expect a relatively smooth morning. The evening commute, however, could be thornier, he said.

That’s when riders on the Yellow and Orange lines could find themselves in trouble if they board a train without checking the destination sign. During Rush Plus hours, some Orange Line trains will still end at New Carrollton, but others will end at Largo Town Center. Similarly, southbound, some Yellow Line trains will terminate at Huntington, but others will end at Franconia-Springfield.

The shift being implemented Monday has been in the works since 2008. Even though Silver Line service is not scheduled to begin until late next year, Sarles wanted to push forward in hopes of improving service sooner for Orange Line riders, Stessel said.

Monday will be the true test for riders, too.

Matt Gardner, a Blue Line commuter, is less than pleased with the coming change. Late last week, he was calculating how to shift his trip to ensure that he could avoid the expected service gap between trains.

Other commuters are expecting quicker trips.

“I would hope I’ll be able to go all the way to Vienna a little faster,” said Ginny Torrise, an Orange Line commuter who works at the Department of Veterans Affairs. “I guess time will tell.”