Everyone keeps saying that, but I have yet to hear these so called "good reasons" not to run the 7k's in 6 car sets. What are they exactly?
I'll leave it to SBJ to be exact, but I believe it has to do with the chance that, if a train of 6 cars had a mechanical failure, than it is more difficult to navigate the train back to the yard because it's missing one of the married pairs that would be part of one of the quads.
WMATA's allegedly reason for running them in only 8 car consists is they don't want to take the risk of having one of the pairs crap the bed on the mainline and end up having to break up the train and move one of the two part of the train back to a yard from the hostler cab.
This reasoning when out the window when people began spotting one or both of the 4 car sets in trains made up with A cars coupled to B cars.
Fact is, I have never heard of WMATA having to break up a train on the mainline to move it back to a yard.
John in the sand box of Maryland's eastern shore.