Complex sentence: Connections to the SEPTA Regional Rail can be made at 30th Street, also a underground passageway connects to the Ex-Pennsylvania Railroad's 30th Street Station to the Market-Frankford Line's 30th Street Subway Station, but has since been seal off due to high crime.
Split into simpler sentences: Connections to the SEPTA Regional Rail can be made at 30th Street. An underground passageway connects the Ex-Pennsylvania Railroad's 30th Street Station to the Market-Frankford Line's 30th Street Subway Station, but this has been sealed off due to high crime.