As I was walking down Market St. today I noticed a train heading into 30th Street that had 3 Silverliner V cars on the front, with two Silverliner IV's trailing. I've never seen this before, is it normal to couple the different sets together? How do the various systems on the trains differ or are they similar, (i.e. doors, announcements, lights, HVAC, etc)?
"Next stop, 34th Street! Exit for University City, Drexel University, and the University of Pennsylvania."