Blue Line riders have long complained that their waiting times are the longest in the system. (Linda Davidson/The Washington Post)

Metro is proposing adding more trains to reduce waiting times for riders on its crowded Blue Line, but the improvements would come at the expense of commuters on four other lines.

Under the proposal, rush-hour Blue Line trains would arrive more frequently — every eight minutes instead of the current 12. But the time between trains on the Orange, Silver, Green and Yellow lines would increase from six minutes to eight.

Blue Line riders have long complained that their waiting times are the longest in the system. Service was reduced to make room for the Silver Line, which opened last July. The proposal also means more trains on the Blue Line at peak times — roughly 56, up from 36.

Metro employees are expected to present the plan Wednesday night at a meeting of the Riders’ Advisory Council.

The change would have to go through a series of public hearings and be approved by the Metro board to take effect. If approved, Metro officials said, the earliest riders could expect the changes would be December.

“This is one option,” said Sherri Ly, a Metro spokeswoman. “Nothing is set in stone. That’s why we go to our riders.”

Ly said the proposed changes are meant to alleviate the bottleneck at the Rosslyn tunnel, which can handle only 26 trains an hour. The change would mean 22 or 23 trains going through the tunnel per hour.

“With that bottleneck, as three different lines are going through there, you have one issue, and it throws everything off,” she said. “If you can eliminate some of those issues, we’re hoping it will improve reliability and on-time train service.”

But word of the changes, first reported by WAMU, caused consternation among riders because they would come on the heels of other actions that have reduced service.

In mid-June, Metro pulled an entire series of rail cars from service for emergency inspection after reports of doors opening while the trains were moving. The 100 4000-series cars were expected to be out of service only several days, but maintenance and engineering employees determined that the work required to bring the cars up to standards would require more time.

That meant the cars would be phased back in over a series of weeks. Without those cars in service, Metro can’t operate the eight-car trains it normally does during rush hours on the Red, Orange, Blue and Green lines.

In addition, Metro also announced that it will sharply cut back on eight-car trains on three lines this summer to permit more maintenance time on the rail fleet’s worst-performing cars. That service reduction will be in effect on Mondays and Fridays through at least Labor Day.

Then there are the daily problems with hot cars, broken escalators and disabled trains. It’s been a particularly bad run of late for Red Line riders.

On Monday, four Red Line trains off-loaded in a span of 16 minutes, turning what should have been a 15-minute commute for some riders into an hours-long nightmare.

“I haven’t seen it this bad in 15 years,’’ said Gus B. Bauman, a lawyer and longtime rider. He was among those caught in Monday evening’s Red Line delays. He described the scene at Metro Center as “complete chaos.”

At one point, the platform at Farragut North was so crowded that Metro had to shut down the fare gates to keep more passengers from entering.

Metro’s on-time performance, according to the most recent Vital Signs tracking report, dropped to 86.7 percent in the first quarter of 2015, compared with 90.5 percent for the same period a year ago.

Many riders likely would be surprised to hear that it’s that high.

“I noticed #wmata’s new rush hour plan to run fewer trains doesn’t include lower fares,” tweeted one rider.

Luz Lazo contributed to this report.