A few more items on this topic. From Washington, DC Post, 6/30/15:
Metro proposes adding more Blue Line trains, but it’d come at a cost for others
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.
More
Another column from Dr. Gridlock in the Washington, DC Post, 7/2/15:
Metro service changes: It’s not just about the Blue Line
Jim Hughes, a senior planning official with the transit authority, outlined the proposal on Wednesday night for the Metro Riders’ Advisory Council. The transit staff’s proposal would set the rush hour gap between trains at eight minutes on the Silver, Blue, Orange, Green and Yellow lines. On all lines but the Blue, that’s a greater gap than under today’s schedule.
Column
And yet another Dr. Gridlock column on 7/6/15:
Metro board to discuss new rail schedule proposal
The proposal itself is dramatic: To make the schedule more reliable, the staff proposes to increase the time between trains on four of those five lines. The scheduled gaps at rush hours would increase from six to eight minutes. The Blue Line would be the exception.
This column
The system went through a few changes on paper before it was decided to run the Silver Line all the way to Largo. Originally the Silver Line was supposed to turn at Stadium/Armory, with only Blue continuing to Largo as it had before. But when that was deemed impossible, the extension of the Silver Line to Largo meant a cut in Blue Line service. It was expected that some Blue Line riders might cry foul. However the way I see it this move would only affect those Blue Line riders who would be travelling from the eastern end to a point in Virginia beyond Rosslyn, since that is where the Blue and Silver split. Passengers between the Maryland stations and the District could take either Blue or Silver trains. So it's hard to understand how relatively few passengers are now driving such a change that will penalize riders on other lines.
Enlarging the headways by reducing frequencies means longer waits at the transfer points (such as L'Enfant Plaza and Metro Center). Anyone who has ridden on weekends when there are often long waits due to construction knows what it's like to stare at those vaulted ceilings hoping to hear the sound of a train coming or feel the rush of air from the tunnel as it draws closer.