SEPTA has no idea how long it will take to fix the problem now sidelining 60 rail cars on the Market Frankford Line (MFL).

But as dire as that might sound, the practical effect seems muted: El trains ran every six minutes during Monday morning’s shortage, instead of their usual four minute headways. Trains were crowded, but not insufferably so. SEPTA set aside 60 buses to fill in for the pulled-cars, but only ended up using eight.

At a press conference Monday, SEPTA General Manager Jeff Knueppel…