First there were signal problems at Harvard. Now, "severe delays in service due to a track problem," specifically, a cracked rail near Central, are creating hordes of refugees. Mamajoan reports  from Porter Square:
Commuters exiting Porter like rats from sinking ship. Buses crammed full, driver waving people on without paying.
Amy Lynne Grzybinski adds :
I've been on the train from Porter for 30 minutes and haven't left Kendall yet. HAHAHA
This is the first time a rail has cracked on the Red Line in almost three weeks .
- Cambridge 
- The T 
- Red Line