The Southeastern Pennsylvania Transportation Authority says the issues started when an inbound train on the Paoli/Thorndale line broke down during the Thursday evening commute. SEPTA says it broke down at a critical point, leading to a switch issue.
In a letter to riders posted on its website, the agency says the problem "cascaded," affecting nearly all of the rail lines. Sixty-eight trains were delayed anywhere from six minutes to nearly an hour.
SEPTA also says it's sorry for taking about 30 minutes to communicate the problem to riders.