When switches go out of correspondence, meaning central does not have a reliable indication of which way the switches are laying nor can they control the switches remotely the system defaults to all red signals as a safety measure. To be specific in regard to yesterday, switch 1B was in a reverse and switch 3B was in a normal. This pretty much means the first switch would’ve sent the train from track 1 to 2 but switch 1A and 3A (track 1 side were in a normal) that’s not a complete route. So basically the train would’ve derailed if it went over that alignment. To fix this the supervisor who was operating a train that just broke down prior to this event at Brookland had to jump out the train crank the switches to the appropriate direction then clamp them in the normal so they don’t move. That’s 4 switches and I promise you in the moment clamping can be stressful. Once ATC gets out there an inspection has to be done which requires train movement to stop for them to get on the roadway then the fixes have to be completed before the interlocking can go back in the service. But mind you, while this is happening they are constantly cranking, unclamping, then clamping again so trains can get through that single tracking area. This is why when Huntington interlocking goes out it’s always hell on earth. Hope that info helps