According to T alerts, Needham, Providence and Franklin Line riders who just want to go home are currently delayed due to "congestion."
MBCR explains that, in this case, "congestion" means an outbound Amtrak train was mistakenly switched onto the Needham tracks, which is sort of like the train equivalent of a truck trying to get on Storrow Drive, given that Amtrak trains use electric power and the Needham Line, well, doesn't.