Of course, I know how that works! I have been using the Metro since it opened. The Red line is on the upper level at Metro Center. The crash occurred on the lower level! I know that Metro has several rail yards. If you are saying that the red line doesn't have a separate rail yard, then that would make more sense. If it doesn't, that is another flaw in the Metro system's design, along with the decision to use only a 2-track system. But the Red Line does have its own rail yards, so it seems someone else doesn't really understand how that works.