WHYY By Assistant Director of Transportation Ken Divers, who leads the vulnerable population task force at SEPTA, walks on the platform at Somerset Station. (Emma Lee/WHYY) SEPTA Police Chief Thomas Nestel stopped at the corner of 15th and Market streets last week on the west side of City Hall. He was on the scene after a man jumped in front of a Market-Frankford Line train at 15th Street Station and died — the third reported suicide on the subway system this year. “Sadly, it’s more common than not,” said the chief. The tragedy is one of several moving SEPTA officials to try out guardrails to decrease the number of falls and jumps onto its tracks.